1Fill a 3 qt. saucepan 2/3 full of water. Over high heat, bring to a boil. Salt the water if you wish. Add the elbow macaroni. Don't cook the pasta for the full amount of time. Reduce the cooking time by 2 minutes. When done, drain and set aside.
2In a medium saucepan, melt 2 T butter over medium heat.
Stir in the flour, whisking together to make a roux. It should look like creamy peanut butter. Cook for 1-2 minutes, just to remove the floury taste. Slowly pour in the milk, whisking to incorporate.
3Add the cheeses, whisking to blend together. Add salt and pepper, stirring constantly, as the cheeses melt and the sauce thickens.
4Spray a 2 qt. casserole with non-stick cooking spray. Pour the cooked pasta into the casserole. Top it with the sauce. Stir to coat the pasta.
Preheat the oven to 350 degrees.
5Bake the mac 'n cheese for 30 minutes. Remove from the oven and add the topping.
Crush the crackers. Crumble the cooked bacon. Melt the remaining 2 T of butter. Mix the crackers and bacon in a small bowl. Pour the melted butter over them and stir to coat. Sprinkle the topping over the mac n cheese. Bake for 30 minutes, til heated through.
If you don't use a cooking spray, you can just lightly oil the casserole dish. It helps with the cleanup.
I do salt my pasta water before I cook the pasta.
I used 4 slices (3 inch x 3 inch) of the cheddar and Monterey jack (I diced them) to equal a 1/2 cup.
You can bake the topping for the full hour if you prefer a crunchy topping. I wanted a softer crumb topping so I baked it for 30 minutes.