Why did my gratin break?

[Chris Hennes]

I made brussels sprout gratin the other night using a recipe from James Peterson's Vegetables. I think I've made it before, but of course I don't recall how it turned out. At any rate, it's basically just sauce mornay (e.g. a Bechamel with cheese) poured over the brussels sprouts and baked. The mornay was fine when I first made it, nice and smooth. But after 30 minutes in a 350°F oven it had broken. It still tasted good, of course, but texturally and visually it was a bit unappealing. Why did this happen, and what can I do to stop it?

[Dave the Cook]

Is it safe to assume that the last time you made it, it came out okay; otherwise you'd have asked this question then?

If the answer to that is "yes," two things spring to mind: 1) did you use a different type of cheese? 2) is there any acid in the recipe? If the answer to (2) is yes, did you remember to add it?

[Chris Hennes]

I have no idea if I used a different type of cheese: I used half parmesan and half sharp cheddar this time. And no, the recipe doesn't call for an acid. Which doesn't mean it doesn't need one to hold together...

[Shalmanese]

Brussel sprouts have a ton of water in them which weeps into the sauce. I find this happens a lot when baking watery vegetables in a bechamel sauce. My theory is that because there's no stirring going on, the water & the bechamel don't mix so you get a broken looking sauce. One tip is to start the cooking of the sprouts/sauce on the stovetop so you can stir and then finish in the oven when the sprouts are starting to get tender.

[Chris Hennes]

I may have exacerbated the "too-much-water" problem in this case, as well, since I blanched them for five minutes first and did not carefully dry them before pouring the sauce over.

[Dave the Cook]

Shalmanese raises good points. The first is, "Was the sauce really broken, or did it just look broken because of free water?" A second related point might have something to do with seasonality. Water content can vary from season to season, plant to plant. or even from specimen to specimen.

Peterson is pretty reliable, so my inclination would be to first look at variables that aren't controllable according to the recipe, before deciding that that recipe (especially one that's worked before) has a flaw in technique or ingredients.

[Chris Hennes]

Well, the sauce was sort of grainy/lumpy: like tiny particles of coagulated cheese sticking to the brussels sprouts. Is that broken?

[JAZ]

When you say "broken," what exactly do you mean? When I think of a cheese sauce "breaking" I think of the oil in the cheese seeping out, usually because of too high a heat. But with a Mornay, you've got flour in there, which should keep than from happening, unless (like I tend to do) you forced a lot of cheese into your Bechamel.

On the other hand, if you mean that you had a layer of water in the finished dish, then the sprouts are the likely culprit. Are they used whole in the dish, or halved, or shredded?

[Shalmanese]

Well, the sauce was sort of grainy/lumpy: like tiny particles of coagulated cheese sticking to the brussels sprouts. Is that broken?

If you have any spare sauce, pour just the sauce in a bowl and whip it to see if it smooths out. If so, it's just free water. If not, I would guess it's milk/cheese proteins coagulating. Did you use the same cheese that Peterson suggests?

[Chris Hennes]

It looked like a protein coagulation problem to me, but I'm not an expert on that: there wasn't freestanding water, it was like the sauce had separated from itself into small particles. I used the amount of cheese that Peterson suggested (2oz cheese to 8oz milk and 4oz cream), and he lists whole bunch that would be OK, including the two I used (parm and cheddar). The sprouts were left whole if they were small, or halved/quartered as necessary to get them to a uniform size for cooking.

[emmalish]

The same thing happened to me the last time I made a cauliflower gratin. I wasn't following any recipe - I just winged it – but the sauce was beautiful before it went in the oven. It didn't separate into oil and solids, but seemed watery and grainy. After reading this thread, I'm inclined to blame water in the cauliflower (which I steamed briefly first).

[JAZ]

I used the amount of cheese that Peterson suggested (2oz cheese to 8oz milk and 4oz cream), and he lists whole bunch that would be OK, including the two I used (parm and cheddar).

I'm curious now -- did you start with a roux and make a bechamel, or just mix the cheese, cream and milk? I've never had good luck heating a cheese sauce for long if there's no flour in it.

[Blether]

I agree with Shalmanese that it sounds like water from the sprouts. Another option is to cook the veg fully, cover with the hot sauce and just grill (broil) to finish.

[Shalmanese]

It looked like a protein coagulation problem to me, but I'm not an expert on that: there wasn't freestanding water, it was like the sauce had separated from itself into small particles. I used the amount of cheese that Peterson suggested (2oz cheese to 8oz milk and 4oz cream), and he lists whole bunch that would be OK, including the two I used (parm and cheddar). The sprouts were left whole if they were small, or halved/quartered as necessary to get them to a uniform size for cooking.

As another wild guess, I would say you went with long aged parmesan and extra sharp cheddar. Older cheeses have a harder time forming a stable sauce. You need something with the binding power to keep the sauce together. Others with more experience in cheese sauces should comment.

[Chris Hennes]

I'm curious now -- did you start with a roux and make a bechamel, or just mix the cheese, cream and milk? I've never had good luck heating a cheese sauce for long if there's no flour in it.

I made a bechamel, then took it off the heat, stirred in the cheese until it was fully incorporated, and then poured it over the sprouts. The parm in this case was a two and a half year old Vacche Rosse since that's all I had on hand. The cheddar was the grocery-store-variety Cabot Extra Sharp. I wonder if maybe I needed to make a thicker bechamel (more flour) to compensate for the non-melting-friendly cheeses? Ordinarily I use Gruyere in gratins, but I didn't have any on hand.

I agree with Shalmanese that it sounds like water from the sprouts. Another option is to cook the veg fully, cover with the hot sauce and just grill (broil) to finish.

That's a good thought too, since I'm already blanching the sprouts I could just finish the job that way, then make a stronger cheese sauce and give it a quick hit from the broiler.

[nickloman]

Surely the real question is why did you make a brussels sprout gratin

[Chris Hennes]

Don't knock it 'till you've tried it... brussels sprout gratin is awesome. This one tasted great, it just looked unappetizing.

[Shalmanese]

I made a bechamel, then took it off the heat, stirred in the cheese until it was fully incorporated, and then poured it over the sprouts. The parm in this case was a two and a half year old Vacche Rosse since that's all I had on hand. The cheddar was the grocery-store-variety Cabot Extra Sharp. I wonder if maybe I needed to make a thicker bechamel (more flour) to compensate for the non-melting-friendly cheeses? Ordinarily I use Gruyere in gratins, but I didn't have any on hand.

It could also be the gratin started boiling in the oven and the cheeses you used would have been stable in a warm sauce but broke down over high heat. Next time, I would pair one sharp cheese (Parmesan/Cheddar) with one melting cheese (Gruyere/Fontina) to buy a bit more insurance.

[Dave the Cook]

Just to be clear: is the recipe written specifically for Brussels sprouts, or is it a generic gratin formula?

[JAZ]

It could also be the gratin started boiling in the oven and the cheeses you used would have been stable in a warm sauce but broke down over high heat. Next time, I would pair one sharp cheese (Parmesan/Cheddar) with one melting cheese (Gruyere/Fontina) to buy a bit more insurance.

I make macaroni and cheese with a variety of cheeses, all based on a bechamel with the cheese added, and always bake it until it's bubbling, and never have this problem. I don't think it's the cheese; I think it's too much water seeping out. The only times I've had cheese in a cream sauce break down from too high a heat, it's been in a sauce without flour.

[Chris Hennes]

Just to be clear: is the recipe written specifically for Brussels sprouts, or is it a generic gratin formula?

I will resist your attempt at clarity: the answer is "both". Which is to say, Peterson has a whole section on general gratin techniques. He then lists out specific recipes for a dozen or so. In his specific recipe he doesn't necessarily list a particular cheese, however, instead referring you to the previous writeup. He does sometimes list a preference, but it's clear that that's not hard and fast. I did not follow his preference in this instance, he likes gruyere, I only had parmesan and cheddar.

[slkinsey]

Parmesan and cheddar are both notorious "graining" cheeses when it comes to sauces. Had you made the sauce with at least one "smooth melting cheese" it probably wouldn't have been a problem. Parmesan, in particular, isn't even considered a "melting cheese."

[Chris Hennes]

You're likely right: Peterson doesn't mention it when he lists out "appropriate cheeses for gratins" so I was hoping that there was enough binding power in the bechamel to hold everything together. Alas, no. So I've picked up some Gruyere to use on this next gratin, it ought to work fine.

[Blether]

I've used sharp cheddar as standard in mornay-based gratins for years. It can go grainy if you put the cheese into the bechamel too early - so that it's in there during the simmer. You can also get a bechamel to go grainy by simmering too fiercely and/or not stirring enough during the simmer.

My grandmother (sorry !) used to make a variation on macaroni cheese (starting with bechamel) using some vinegar (a tbsp for a family-size dish ? who knows) when she mixed it all together, that ended up extremely grainy, on purpose.

Didn't Marcella Hazan say that the beauty of parmesan is that it melts with absolutely no stringiness ?

[Chris Hennes]

It's interesting, I re-read the Peterson page on cheese, and his top choice is Parmesan. I've never had any trouble with it melting into an "Alfredo"-type sauce, or adding it to a bechamel, so I figure it must be the extra heat in the oven that is the issue. So I made another gratin this week (broccoli and bacon...mmmm) and it turned out very well, using parmesan and gruyere, and being careful to dry off the broccoli before adding the mornay. Dunno which of those changes did the trick...