Sautéed Mushroom Filling with Thyme

Heat 1 tablespoon butter in medium skillet over medium heat until foaming; add 1 small shallot, minced (about 1 tablespoon), and cook until softened and just beginning to color, about 2 minutes. Add 2 medium white mushrooms (about 2 ounces), cleaned and sliced 1/4 inch thick. Cook, stirring occasionally, until softened and lightly browned, about 3 minutes. Off heat, stir in 1 teaspoon fresh minced thyme leaves and salt and pepper to taste; transfer mixture to small bowl and set aside until ready to use.