Same way you'd thicken gravy itself. Use a roux. Mix equal parts flour and butter (oil or crisco if you prefer) and brown in a little pan. Lighter colored rouxs give you thicker gravies and sauces. A roux is equal parts butter and flour? Who knew? Apparently everyone but me To be utterly technical, a roux is the cooked version. The uncooked version of equal parts butter and flour, uncooked, is a beurre manie. another way to thicken the sauce in stews that doesn't resort to rouxs or slurries (or reduction, if reducing too much will make the sauce bitter), is to take out some of the vegetables (you may wish to add a few more to begin with), puree them in a blender, then add the puree back into the stew. ok, then here's another stupid question. Do you melt the butter first and add the flour to it and mix together, or do you add each part to the sauce separately? If you mix the flour with softened butter, you've got "beurre manié." You pinch off bits of it and stir it well into the sauce to be thickened. You can add it little by little, letting each addition cook, before adding the next bit. This is different from a roux, for which you melt the butter, stir in the flour and cook it to the desired color, and then add the liquid (or if you're making gumbo, adding the cooked roux to the liquid). Beurre manié is easier to use, IMO, when thickening sauces that are already there in the pot. And you can made up a batch of it to keep in the fridge or freezer in small balls, for whenever you need it. ← ←