Preheat broiler and place a large pot of salted water over high heat to boil.
Once the water is boiling, toss in the pasta and cook to al dente, according to package directions. Drain and reserve it in the pot it was cooked in.
While the pasta is cooking, melt the butter in a large skillet over medium-high heat. Add the onion and cook until tender, 2-3 minutes.
Stir in the flour and cook for about 1 minute. Whisk in the milk, then add some salt and freshly ground black pepper along with the Dijon mustard, Worcestershire sauce and hot sauce. Simmer until thickened, 2-3 minutes. Remove the pan from the heat and stir the cheeses into the sauce in a figure-eight motion. Cover the pan and keep the sauce warm over low heat.
Place a large skillet over high heat with the EVOO. When the oil is hot, toss in the scallops and shrimp, season with salt and freshly ground black pepper and add in the grated garlic. Cook about 2 minutes, until the seafood is just opaque in color - they will cook some more in the oven so be careful not to overcook them on the stovetop.
Toss the shrimp and scallops into the pot with the cooked pasta and pour in the cheese sauce. Stir to evenly incorporate everything, and then divide the mixture between four medium-size ramekins. Place the ramekins onto a small sheet tray.
In a small bowl, combine the breadcrumbs, Parmigiano and parsley. Sprinkle the mixture evenly over each portion of seafood mac and place them under the broiler to brown the top, about 2 minutes.
Serve a ramekin of the seafood mac alongside Mini Meatloaves With Tomato-Balsamic Gravy.