Return the mushroom broth to a pot over high heat and reduce until it equals about 2 cups.

Stir in the mushroom broth, bring to a boil and then simmer for about 10 minutes, so that it reduces by 1/3.

When you're ready, heat the chicken stock and mushroom broth to a simmer.

Add a small amount of the mushroom broth, whisking vigorously to keep mixture smooth.

Pour the mushroom broth into a saucepan and simmer over medium heat until reduced by half, about 30 minutes.

Add the mushroom broth, cover and simmer for 40 minutes.

Add the mushroom broth, all of the mushrooms, the salt and pepper.

In a large skillet, warm the mushroom broth over medium heat.

Combine the mushroom broth and mustard in a food processor or blender.

Begin adding mushroom broth a little at a time, stirring until it is absorbed.