Add pasta to large stockpot of boiling water and cook 4 minutes, or until slightly firmer than al dente. (Boil for 1 minute less than the cooking time listed on the package.) Drain and set aside. Do not rinse.
Sauté vegetables:
In the meantime, add butter to a large, oven-safe skillet over medium heat. Stir in shallot and cook 2 minutes, or until softened. Stir in broccoli and asparagus and cook 4 minutes, or until the color turns bright green. Stir in green peas and spinach and cook 2 minutes, or until spinach is wilted. Season with salt and pepper to taste. Remove cooked vegetables from skillet and set aside.
Prepare sauce:
Add butter to same skillet used to cook vegetables. Stir in milk and mashed beans and whisk over medium heat until the texture is smooth and creamy. Stir in onion powder, crushed red pepper, and salt and pepper. Reduce heat to low and simmer 10 minutes, or until sauce is thickened and reduced.
Stir in shredded cheddar cheese and shredded mozzarella cheese and turn off heat. Add cooked pasta and vegetables to the sauce in the skillet. (Depending on the size of your skillet, you may need to stir in a separate pot or bowl before transfering the mixture back into the skillet to thoroughly mix the components.)
Make topping (if using):
Preheat broiler. Stir together breadcrumbs, softened butter, dry basil or oregano (if using), and salt and pepper.
Sprinkle breadcrumb topping over mac and cheese skillet. Broil 2 minutes, or until topping turns golden brown.
Remove from oven and garnish with chopped fresh herbs and crushed red pepper if desired.
Notes
Substitute with seasonal vegetables as needed to make this recipe year round. Sauté 3 cups of chopped seasonal vegetables with shallot (or onion) and spinach (or any greens).