Langostino Macaroni and Cheese

Wow. This is absolutely amazing. Decadent (definitely not healthy!), rich, and oh-so-satisfying. It would be perfect for a romantic evening, but it was just as perfect for a relaxing Sunday night in our house!
1 box macaroni, cooked and drained
1 Tbsp. olive oil
1 onion, chopped
4 small garlic cloves, minced
3 Tbsp. butter
3 Tbsp. flour
1 cup FF milk
1 cup FF half-and-half
1-1/4 cups reduced-fat cheddar cheese
1/2 cup Parmesan cheese
1/2 cup mozzarella cheese
1 10 oz. package langostino, defrosted according to package directions
1 tsp. Old Bay seasoning (I didn't have any of this, but it would really be fantastic in this!)
1/4 tsp. cayenne pepper
Sale and pepper to taste

Preheat oven to 375 degrees. Spray a large casserole dish with nonstick cooking spray.

Heat olive oil in large saucepan over medium heat until oil starts to ripple. Add onion and saute until tender, about 3 minutes. Add garlic and saute until fragrant, about 30 seconds. Add butter to pan and stir to combine with onions and garlic. When butter is melted, whisk in flour to make a roux. When combined, add milk and half-and-half and whisk until combined. Allow mixture to thicken.

When milk mixture has thickened, add spices and cheeses and stir until the cheese is melted. Add langostino meat and stir to combine. Mix with pasta and pour into casserole. Bake uncovered until top is browned and sauce is bubbling, about 15-20 minutes.