Prepare Herbed Croutons. Meanwhile, in a Dutch oven heat oil over medium heat. Add prosciutto; cook and stir until browned and crisp. Drain on paper towels, reserving drippings in Dutch oven. Add leeks to reserved drippings; cook and stir 4 minutes or until softened. Add garlic; cook and stir 1 minute more.
Add next eight ingredients (through crushed red pepper). Bring to boiling, stirring occasionally. Reduce heat. Simmer, covered, 30 minutes, adding Brussels sprouts the last 5 minutes.
Remove and discard bay leaf. Stir in basil and/or parsley and half of the croutons; let stand 5 minutes. Sprinkle servings with cheese, prosciutto, and remaining croutons.
Preheat oven to 350 degrees F. Spread bread cubes in a single layer on a baking sheet. Bake for 10 minutes.
Meanwhile, in a blender combine remaining ingredients. Cover and blend until mixture is smooth.
Transfer the hot bread cubes to a large bowl. Spoon mixture over bread cubes; toss to coat evenly with herb mixture. Return the bread cubes to the baking sheet and bake 13 to 15 minutes more or until crisp and golden around the edges, stirring once halfway through baking.