Step 1Heat the oven to 350 degrees. Cook the macaroni in plenty of rapidly boiling salted water until done, about 10 minutes. Drain well and set aside.
Step 2Melt the butter and saute the onion and garlic until soft, about 5 minutes. Whisk in the flour to make a roux. Cook until mixture is smooth, about 5 minutes. Whisk in the milk and the cream and simmer until the mixture is thick and creamy, about 15 minutes.
Step 3Add the garlic, mustard, Jack, 1 cup of Cheddar, Parmesan and 1/2 cup blue cheese. Return to the heat till melted. Add a dash of hot sauce and salt and pepper to taste.
Step 4Mix the sauce with the cooked macaroni and put in a 13x9-inch baking dish. Sprinkle the reserved 1/2 cup of Cheddar and 1/4 cup blue cheese on top and bake until brown and crusty on top, about 30 minutes.