For pasta:

• 1 16-ounce package of spaghetti
• 2 tablespoons unsalted butter
• 1 cup grated parmesan cheese
• 1 teaspoon kosher salt
• 1 tablespoon freshly ground pepper
• 2 large eggs, beaten

For Sauce:

• 1 tablespoon olive oil
• 1 medium onion, chopped (about 2 cups)
• 1 green bell pepper, chopped
• 1 1/2 lbs sweet Italian sausage, crumbled
• 1 (24-ounce) jar arrabbiata sauce, preferably Rao’s
• 1 teaspoon granulated sugar
• 1/2 teaspoon dried oregano
• 1/2 teaspoon garlic salt

For Bechamel: 

• 1/4 cup unsalted butter
• 1/4 cup all-purpose flour
• 2 cups whole milk, warmed
• 1/2 cup grated parmesan cheese
• Kosher salt and pepper

To Finish:

• 6 ounces shredded mozzarella cheese
• 2 tablespoons unsalted butter
• 1 cup panko breadcrumbs
• Chopped parsley, for garnish