Step 1
Bring a large pot of lightly salted water to a rolling boil. Cook pasta shells at a boil until tender but still slightly firm about 10 minutes; drain and set aside.
Step 2
Preheat the oven to 375 degrees F (190 degrees C).
Step 3
Grease a 9x13-inch casserole dish.
Step 4
Melt 2 tablespoons margarine in a skillet over medium heat. Cook and stir shallot in melted margarine until lightly browned about 5 minutes.
Step 5
Whisk flour into margarine and shallots to form a smooth paste.
Step 6
Slowly whisk evaporated milk into flour mixture until it forms a smooth sauce; simmer until thickened 2 to 4 minutes.
Step 7
Whisk shredded Cheddar cheese and mascarpone cheese into sauce until cheeses have melted about 5 minutes.
Step 8
Stir pumpkin puree lemon zest salt black pepper garlic powder paprika nutmeg and hot sauce into the sauce until combined.
Step 9
Lightly mix in lobster tail meat green peas and cooked pasta shells until heated through about 5 minutes.
Step 9
Pour pasta mixture into prepared casserole dish; top with panko crumbs and Parmesan cheese. Drizzle 2 tablespoons of melted margarine over the casserole.