From https://www.westonaprice.org/health-topics/food-features/broth-is-beautiful/#gsc.tab=0

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SAUCE BASICS

Meat sauces are made from stocks that have been flavored and thickened in some way. Once you have learned the technique for making sauces—either clear sauces or thick gravies—you can ignore the recipe books and be guided by your imagination.

Reduction Sauces are produced by rapid boiling of gelatinous stock to produce a thick, clear sauce. The first step is to “deglaze” coagulated meat juices in the roasting pan or skillet by adding 1/2 cup to 1 cup wine or brandy, bringing to a boil and stirring with a wooden spoon to loosen pan drippings. Then add 3 to 4 cups stock, bring to a boil and skim. (Use chicken stock for chicken dishes, beef stock for beef dishes, etc.) The sauce may now be flavored with any number of ingredients, such as vinegar, mustard, herbs, spices, fresh orange or lemon juice, naturally sweetened jam, garlic, tomato paste, grated ginger, grated lemon rind, creamed coconut, whole coconut milk or cultured cream. Let sauce boil vigorously, uncovered, until reduced by at least one half, or until desired thickness is achieved. You may add about 1-2 teaspoons gelatin to promote better thickening, although this should be avoided by those with MSG sensitivities (as gelatin contains small amounts of MSG). Another way to thicken is to mix 2 tablespoons arrowroot powder with 2 tablespoons water. Gradually add this to the boiling sauce until the desired thickness is obtained. If sauce becomes too thick, thin with a little water. The final step in sauce-making is to taste and add sea salt if necessary.

Gravies are thickened with flour rather than by reduction. They are suitable for meats like roast chicken and turkey, which drip plenty of fat into the pan while cooking. After removing the roasting fowl and roasting rack, place pan on a burner. You should have at least 1/2 cup good fat drippings—if not, add some butter, goose fat or lard. Add about 1/2 cup unbleached flour to the fat and cook over medium high heat for several minutes, stirring constantly, until the flour turns light brown. Add 4 to 6 cups warm stock, bring to a boil and blend well with the fat-flour mixture, using a wire whisk. Reduce heat and simmer 10 minutes or so. Check for seasonings and add sea salt and pepper if necessary. You may also add herbs, cream, butter, whole coconut milk or creamed coconut.