PreparationFor mushroom topping: Melt butter in large skillet over medium-high heat. Add mushrooms and thyme. Sauté until browned, about 8 minutes. Season with salt and pepper. DO AHEAD: Can be made 1 day ahead. Cover; chill. Rewarm before using. For thyme vinaigrette: Blend first 4 ingredients in blender 10 seconds. With machine running, gradually add 1/2 cup olive oil; blend until almost smooth. Season to taste with salt and pepper. Preheat oven to 400°F. Arrange bread on rimmed baking sheet. Brush with oil. Bake until beginning to crisp, about 8 minutes. Mound 1/4 cup mushrooms on each bread slice. Drizzle each with thyme vinaigrette, then sparingly with truffle oil.
PreparationFor mushroom topping: Melt butter in large skillet over medium-high heat. Add mushrooms and thyme. Sauté until browned, about 8 minutes. Season with salt and pepper. DO AHEAD: Can be made 1 day ahead. Cover; chill. Rewarm before using. For thyme vinaigrette: Blend first 4 ingredients in blender 10 seconds. With machine running, gradually add 1/2 cup olive oil; blend until almost smooth. Season to taste with salt and pepper. Preheat oven to 400°F. Arrange bread on rimmed baking sheet. Brush with oil. Bake until beginning to crisp, about 8 minutes. Mound 1/4 cup mushrooms on each bread slice. Drizzle each with thyme vinaigrette, then sparingly with truffle oil.