Cook elbow pasta according to package al dente, around 7-8 minutes. Remove from heat, drain and set aside. 

Add the butter in an oven safe skillet and melt butter over medium heat. Add flour and stir constantly for about 30 seconds to allow butter to absorb into flour. Add the milk and stir constantly until the mixture slightly thickens. Remove skillet from heat and slowly add in 1 1/2 cups of the shredded Pepper Jack cheese, stirring it as you add it until all the cheese has been melted and the sauce becomes smooth.

Stir in cooked elbow pasta. Top with remaining Pepper Jack cheese. You can also slice a jalapeno or serrano and add it to the top too! 

Place skillet in oven and bake at 350° for 20-25 minutes until cheese is slightly golden. Remove from oven and enjoy.