Preparation Heat 2 tablespoons butter in a 12-inch heavy nonstick skillet over moderately high heat until foam subsides, then cook mushrooms with salt and pepper, stirring occasionally, until liquid mushrooms give off is evaporated, about 8 minutes. Add wine and boil, stirring occasionally, until liquid is evaporated, about 5 minutes. Cool mushrooms to room temperature, about 10 minutes. Toss mushrooms with cheese and parsley in a bowl. Divide cheese mixture among 8 slices of bread (a scant 1/2 cup per slice), spreading evenly, then top with remaining 8 slices. Heat 1 tablespoon butter in cleaned skillet over moderate heat until foam subsides, then cook 2 sandwiches, without turning over, until undersides are browned, about 3 minutes. Transfer sandwiches to a cutting board. Heat 1 tablespoon butter in skillet until foam subsides, then return sandwiches, browned sides up, to skillet and cook until undersides are browned, about 3 minutes more, transferring back to cutting board as cooked. Make 3 more batches in same manner. Trim off crusts and cut each sandwich into 4 triangles. Top each triangle with a drop of truffle oil (if using). Cooks' note:
Preparation Heat 2 tablespoons butter in a 12-inch heavy nonstick skillet over moderately high heat until foam subsides, then cook mushrooms with salt and pepper, stirring occasionally, until liquid mushrooms give off is evaporated, about 8 minutes. Add wine and boil, stirring occasionally, until liquid is evaporated, about 5 minutes. Cool mushrooms to room temperature, about 10 minutes. Toss mushrooms with cheese and parsley in a bowl. Divide cheese mixture among 8 slices of bread (a scant 1/2 cup per slice), spreading evenly, then top with remaining 8 slices. Heat 1 tablespoon butter in cleaned skillet over moderate heat until foam subsides, then cook 2 sandwiches, without turning over, until undersides are browned, about 3 minutes. Transfer sandwiches to a cutting board. Heat 1 tablespoon butter in skillet until foam subsides, then return sandwiches, browned sides up, to skillet and cook until undersides are browned, about 3 minutes more, transferring back to cutting board as cooked. Make 3 more batches in same manner. Trim off crusts and cut each sandwich into 4 triangles. Top each triangle with a drop of truffle oil (if using). Cooks' note: