Preheat the oven to 425 degrees F.
Heat a medium size pot on medium heat and add butter. Stir the butter around the pot until it's melted. Add flour and stir continuously.
When the butter and flour start to thicken (about 2 minutes), add milk and stir. Stir in granulated garlic and salt. Remove the white sauce from the heat and set aside for a moment.
In a medium size casserole dish, add the cooked pasta. Pour the white sauce over the pasta and stir together to coat the pasta.
Add half of the cheese to the pasta and white sauce mixture. Stir so that the cheese is mixed in with the pasta and white sauce.
Top the pasta mixture with the remaining cheese. Bake in a preheated oven until the cheese melts (about 15 minutes).
By this time the sloppy joe mixture should be reduced to a thick but saucy consistency.
Assemble and serve while both are hot; in serving dishes, add a layer of the sloppy joe mixture, then a layer of macaroni and cheese, and repeat. Garnish with thinly sliced jalapenos.