Bring a pot of salted water to a boil for the pasta. Cook the pasta 2 minutes less than instructed on its packaging.

Heat a large skillet or saucepan over medium heat. Add the butter and melt. Add the flour to the melted butter and cook/stir for 30-60 seconds until you have a thick paste that smells slightly toasty.

Add the milk and use a rubber whisk (for nonstick pans) or spatula to mix everything together. Continue cooking and stirring until no lumps remain and you have a thick mixture that leaves a trail when you drag your spatula/whisk across the bottom of the pan.

Add half the cheese, stirring until evenly melted. Add the remaining cheese and stir until smooth. Reduce the heat to low.

Add the paprika, cajun seasoning, and black pepper. Stir well before adding the chopped peppers, Greek yogurt, and dijon mustard. Cook for another 30-60 seconds until you have a smooth sauce.

Drain the cooked pasta and add to the cheese sauce, gently folding everything together. Serve with fresh chopped parsley, if desired.