1 loaf (1-lb.) French baguette bread, 24" by 4" 1/2 c. butter, softened 2 Tbsp. chopped onion 1 Tbsp. poppy seeds 1 tsp. seasoned salt 1/2 tsp. lemon juice 1 Tbsp. prepared mustard 1 4-oz. can mushrooms stems and pieces, drained and chopped 1-lb. (4 cups) Chalet Swiss Cheese, shredded
Preheat oven to 350° F. Slice bread at 1 1/2-inch intervals without cutting through the bottom crust. Cut the loaf lengthwise across the top, perpendicular to the other slices, again not slicing through the bottom loaf. Set aside. Mix the remaining ingredients, except the cheese, in a large mixing bowl. Stir in cheese. Spread the filling between the slices. Wrap loaf in aluminum foil, sealing all ends, and place on baking sheet. Bake for 30 to 40 minutes. Serve warm.