1 4-x-16-inch loaf French bread
2 tablespoons olive oil
8 ounces sweet or hot Italian sausage
1 cup yellow onion, sliced
4 cups (6 ounces) fresh baby spinach
1 cup grape tomatoes, halved
1/2 teaspoon red chile flakes, optional
1 cup (about 8 ounces) Wisconsin Fresh Mozzarella, cubed
1/2 cup (2 ounces) Wisconsin Aged Provolone or Parmesan, shredded
6 tablespoons pizza or marinara sauce
Preheat oven to 400°F.
Slice the top quarter from bread. (Reserve slice for another use.) Remove bread from bottom, hollowing loaf and leaving 1/2- to 3/4-inch border with crust. Place bread on baking sheet. Brush inside with olive oil and bake 5 minutes, or until edges are golden and bread is slightly dry.
Remove casing from sausage. Place sausage in skillet, breaking up into small pieces, and cook until almost browned. Add onions. Cook 4 minutes, until onions soften. Add spinach, in batches if necessary, and cook 2-3 minutes, until spinach is wilted. Remove from heat.
Add tomatoes, chile flakes, Mozzarella and Provolone to sausage mixture. Stir well.
Spread bread with pizza sauce. Fill with sausage-cheese mixture. Bake 20 minutes or until ingredients are heated through and cheese melts.