Pumpkin Lobster Mac and Cheese

1 (12 ounce) package uncooked shell pasta

2 tablespoons margarine

1 tablespoon minced shallot

1 tablespoon all-purpose flour

1 (12 fluid ounce) can evaporated milk

1 (8 ounce) package shredded Cheddar cheese

1 (8 ounce) container mascarpone cheese

1 cup canned pumpkin puree

1 teaspoon lemon zest

salt and ground black pepper to taste

1 pinch garlic powder, or to taste

1 pinch paprika, or to taste

1 pinch ground nutmeg, or to taste

2 dashes hot sauce, or to taste

1 pound cooked lobster tails, peeled and chopped

1 (12 ounce) package green peas, thawed if frozen

½ cup panko bread crumbs

⅓ cup grated Parmesan cheese

2 tablespoons margarine, melted

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.

Preheat the oven to 375 degrees F (190 degrees C).

Grease a 9x13-inch casserole dish.

Melt 2 tablespoons margarine in a skillet over medium heat. Cook and stir shallot in melted margarine until lightly browned, about 5 minutes.

Whisk flour into margarine and shallots to form a smooth paste.

Slowly whisk evaporated milk into flour mixture until it forms a smooth sauce; simmer until thickened, 2 to 4 minutes.

Whisk shredded Cheddar cheese and mascarpone cheese into sauce until cheeses have melted, about 5 minutes.

Stir pumpkin puree, lemon zest, salt, black pepper, garlic powder, paprika, nutmeg, and hot sauce into the sauce until combined.

Lightly mix in lobster tail meat, green peas, and cooked pasta shells until heated through, about 5 minutes.

Pour pasta mixture into prepared casserole dish; top with panko crumbs and Parmesan cheese. Drizzle 2 tablespoons of melted margarine over the casserole.

Bake in the preheated oven until topping is brown and crisp, 40 minutes.