Four-Cheese Mac With Bacon
1 • medium white onion, finely chopped
5 1/2 cups • whole milk (do not use skim)
1 1/2 cups • grated parmesan cheese (about 4 ½ ounces)
1 1/2 cups • grated Gruyere cheese (about 6 ounces)
1 1/2 cups • grated Fontina cheese (about 6 ounces)
Heat oven at 375 degrees. Butter a 3-quart casserole dish. Fry bacon slices; set on paper towels. Pour off all but approximately 3 tablespoons of the bacon grease. Put pan back on medium heat and add onion. Cook about 5 minutes, until softened. While stirring constantly, add about a third of the flour; continue stirring and slowly adding flour, for at least 1 minute.
Transfer onion/flour mixture to a large, heavy saucepan on medium heat. While whisking, slowly pour in milk. Cook while whisking until mixture bubbles and gets thicker (not necessarily “thick”). Remove pan from heat. Add salt, pepper, cayenne pepper, the cheeses and stir. Crumble bacon and add it, stirring. Set aside.