Add 5 tablespoons (75 milliliters) tomato purée to 1½ cups (375 milliliters) demi-glace. Simmer the sauce gently for 10 minutes. Skim off any scum or froth that floats to the surface. Add 2 tablespoons (30 milliliters) duxelles and 2 ounces (50 grams) ham cut into small cubes (brunoise). Finish the sauce with 1 teaspoon (5 milliliters) each chopped parsley, chervil, and tarragon.