"This is a creamy, rich, and decadent recipe for an 'over the top' addition to any meal.
After years of making basic mac and cheese, this version with shrimp and lobster is an indulgence worth making for those special to you. It is an adapted recipe from strong Southern women (Patti LaBelle, Mama Jean, and my son's girlfriend Ashley)...all wonderful foodies! I make this a day ahead."
Bring a large pot of lightly salted water to a boil. Cook elbow macaroni and 1/2 cup dried onion in the boiling water, stirring occasionally, until macaroni is tender yet firm to the bite, about 8 minutes. Drain.
Place lobster and shrimp in a colander. Pour the cooked pasta and onions over shellfish; let drain.
Preheat the oven to 375 degrees F (190 degrees C).
Warm evaporated milk and cream slowly in a saucepan over medium-low heat. Whisk in flour. Whisk eggs together in a small bowl.
Cook sauce until small bubbles form. Add sauce very slowly, 1/4 cup at a time, to the bowl with the eggs, being careful not to cook and scramble the eggs. Slowly mix the egg-cream mixture back into the pan. Continue cooking on medium-low heat, stirring occasionally, until thick and smooth, 5 to 10 minutes.
Melt 1 stick of butter in the pot used to cook the pasta over medium heat. Add flour; cook until roux thickens and turns caramel in color, about 5 minutes. Stir in Cheddar cheese, Swiss cheese, and Monterey Jack cheese. Cook, stirring constantly, until mostly melted, about 4 minutes. Pour in the cream sauce and stir until smooth.
Stir pasta, lobster, and shrimp into the cheese and cream sauce to coat completely. Pour mac and cheese into a 9x11-inch baking dish.
Melt another stick of butter in the saucepan used to make the sauce. Add onion seasoning and herbes de Provence; stir. Add crackers. Cook and stir over medium heat until coating mixture is lightly toasted, about 5 minutes.
Cover mac and cheese with thin pats of butter. Top with the cracker coating.
Bake in the preheated oven until top is crispy and cheeses are melted, about 1 hour.