More pastry cream problems

[piracer]

So i made another batch of pastry cream and something strange and bad happened: after tempering the yolks and pouring it back into a stainless steel pot, i began whisking it over heat to cook the cream. It a.) never got thick b.) created a 'foam' on top with a liquid below (clearly the fat just separated out) c.) when i tasted it, it had a nasty metallic flavor to it.

Now the recipe wasn't exactly what I've made before but the proportions weren't that much off and the general technique is the same. In to a bowl: yolks, sugar, cornflour, mixed and then heated milk flavored with vanilla added in.

So why the separation of fat (i did however use a little cream mixed into my milk as it wasn't whole milk but i've done this before to compensate for the fat content and it was fine) But more importantly, where did that nasty metallic flavor come from?

[Eastgate]

This sounds like a broken emulsion. It happens. Assuming you didn't scramble the yolks, you can fix it like a broken holland aisle -- another yolk, beat with some water, add in the broken sauce.

On the metallic taste: if this was a broken emulsion, the sugar would all be in the water layer. Ditto the starch. So the top layer would be egg, milk fats, and vanilla. I'd check that vanilla: how old is it? What does it taste like?

[TheTInCook]

What kind of pot were you using? Aluminum?

[pastrygirl]

Crazy. Maybe the milk was past its prime? I've had some separation a few times when heating the milk, water, and butter for pate a choux, and figured maybe the milk was old but continued anyway. Separated pastry cream isn't going to fix itself, so you have more of a problem.

This happened after adding the yolks and starch? How much did you deviate from your usual proportions?

[piracer]

The vanilla wasn't that old but i guess if that was the layer it would explain the nasty taste. The milk wasn't exactly the freshest but i tasted it before cooking and it tasted fine. Also the pot was stainless steel, and im pretty sure the whisk was too. Finally i dont think i deviated that much from the usual proportions, i think maybe half a yolk more then the recipe counted for (since it was halved and the it was like 5 yolks and i used 3).

I think the thing i did do different was adding the yolks sugar and starch at the same time. I think you were supposed to beat the yolks with sugar first, a little milk THEN starch, but how does that change things since when tempering the yolks it came to a consistency that seemed normal.