In a large pot, bring salted water to a rolling boil over high heat. Add elbow macaroni and cook until al dente, about 7-8 minutes. Drain and set aside.

In a medium saucepan, melt 2 tablespoons of unsalted butter over medium heat. Whisk in 2 tablespoons of all-purpose flour for about 1 minute until smooth.

Slowly pour in 1 cup of whole milk while whisking vigorously to prevent lumps. Cook for 2-3 minutes until thickened.

Stir in 1.5 cups of sharp cheddar cheese and 0.25 cups of mozzarella cheese, along with mustard powder, garlic powder, salt, and black pepper. Stir until fully melted and smooth.

Gently fold in the cooked macaroni, ensuring every piece is coated with the cheese sauce. Mix for about 1-2 minutes.

In a skillet, melt a small pat of butter over medium heat. Spread a generous portion of mac and cheese on half of a flour tortilla, then fold it over.

Cook each quesadilla for 2-3 minutes on each side until golden brown and crisp.

Remove from the skillet, let rest for a minute, slice into wedges, and serve warm.