Prepare the Mushrooms: Clean the mushrooms with a damp cloth and slice them evenly to ensure even cooking.
Melt the Herb Butter: In a large skillet, melt 2 tablespoons of unsalted butter over medium heat. Once melted, add the minced garlic and sauté for 1-2 minutes until fragrant but not browned.
Sauté the Mushrooms: Add the sliced mushrooms to the skillet, stirring to coat them in the garlic butter. Cook for about 5-7 minutes until the mushrooms are golden brown and have released their moisture. Stir occasionally for even cooking.
Season and Add Herbs: Sprinkle in the fresh thyme, parsley, and chives. Season with salt and pepper to taste, and cook for another minute until the herbs become fragrant.
Toast the Bread: While the mushrooms are finishing, toast the rustic bread slices until they are golden and crispy. You can do this in a toaster, under a broiler, or in a separate skillet with a little butter until crispy.
Assemble the Toasts: Spread the remaining 2 tablespoons of butter evenly on the toasted bread. Top each slice generously with the sautéed mushroom mixture.
Garnish and Serve: If desired, sprinkle freshly grated Parmesan or crumbled goat cheese on top of the toast. Serve warm, garnished with additional herbs if you like.