Always follow the recipe, but if experimenting, creating, or adjusting a recipe to your liking, you can follow the below guidelines for gravies, sauces, cream-bases, and roux.
Basics
To thicken liquid for a basic gravy, sauce, cream-base for casseroles, or roux for soups, follow these basic measurements:
2 Tbsp fat, grease, oil, or butter : 2 Tbsp flour : 1 cup liquid (broth, milk, or combination)
You will also want to add salt, pepper, and seasonings most of the time. For basic gravy, use 1/3 tsp salt and 1/16 tsp pepper for 1 cup gravy. You may adjust this to your taste.
Salt and pepper for larger quantities: I use 1 1/2 tsp salt and 1/4 tsp pepper per 4 cups.
For pan gravies, fry your meat first. Remove meat from skillet. Leave cracklings, oil or grease, etc in the pan. You may need to add a little butter or oil if there is not enough left (or remove some if there is too much). Brown flour directly in oil used to fry the meat, loosening cracklings and browned bits. Proceed from there.
If you breaded your meat before frying, you may want to reduce the amount of flour or add a little extra liquid.
Variations
Sometimes you will want a thinner sauce or gravy. If you want it thinner, reduce the amount of flour and fat/grease/oil/butter by the same amount.
Sometimes you will want a thicker sauce or gravy. If you want it thicker, increase the amount of flour and fat/grease/oil/butter by the same amount.
Soups: If you will not be combining the roux with straight broth or liquid later in the recipe, use 1 Tbsp flour instead of 2 for soups. For a very thick soup or chowder, you may want to use 1 1/2 Tbsp flour.
Pan Gravy: Fry your meat first. Remove meat from skillet. Leave cracklings and oil or grease, etc in the pan. You may need to add a little butter or oil if there is not enough left (or remove some if there is too much).
Brown flour directly in oil used to fry the meat, loosening cracklings and browned bits. Proceed from there.
If you breaded your meat before frying, you may want to reduce the amount of flour or add a little extra liquid at the end, if gravy comes out too thick.
Cheese: If you will be adding cheese to your casserole, soup, or sauce, you will want to reduce the amount of flour, as the cheese will also thicken the resulting sauce. Depending on the amount of cheese to be added later, reduce to flour to either 1 or 1 1/2 Tbsp per cup of liquid. If you are substituting your own cream base for cream of soup in a recipe, follow the below instruction regardless of cheese.
Substituting for Cream of Soup in Casseroles
You can substitute your own cream-base for cream of soups in casserole recipes.
To do this, first figure out how much soup + liquid the recipe will end up with. 1 can of soup is 10 3/4 oz. Usually, recipes call for you to add 1 cup (8 oz.) of milk or broth to this. So, the total base would be 18 3/4 oz or approximately 2 1/3 cups. Use your judgement on whether to aim for this exactly, round down to 2 cups or round up to 2 1/2 cups. Casseroles are forgiving.
Below are some starting points for replacing cream of soups in casseroles. These measurements will work well for 2 quart casseroles:
1 can Cream of Mushroom Soup + 1 cup milk
4 Tbsp butter : 2 1/2 Tbsp flour : 1/2 tsp salt : 1/16 tsp pepper : 2 to 2 1/2 cups milk
1 can Cream of Mushroom Soup + 1 cup broth
4 Tbsp butter : 2 1/2 Tbsp flour : 1/2 tsp salt : 1/16 tsp pepper : 1 to 1 1/2 cups milk : 1 cup broth
1 can Cream of Chicken Soup + 1 cup milk
4 Tbsp butter : 2 1/2 Tbsp flour : 1/2 tsp salt : 1/16 tsp pepper : 1 to 1 1/2 cups milk : 1 cup chicken broth
- Melt butter over medium heat in whatever pot, pan, or skillet you will need for the remainder of the recipe.
- Add flour, salt, and pepper to melted butter.
- Cook, stirring constantly, until golden brown and flour smells toasted*.
- Pour liquid(s) over this. Bring to a boil, stirring constantly.
- Cook, stirring constantly, until thickened -OR- reduce heat to low and simmer until desired consistency**.
- Use this in place of cream of soup + liquid in recipe and continue from there.
Notes
*The longer you brown the flour, the darker and richer your gravy will be.
**The longer you cook it, the thicker it will get.