01 - Melt butter in a medium saucepan over medium heat. Add flour and whisk constantly for 1 minute to form a roux, cooking until smooth but not browned.
02 - Gradually whisk in the milk. Cook, stirring frequently, until mixture thickens and reaches a gentle simmer, approximately 2 to 3 minutes.
03 - Reduce heat to low. Add Dijon mustard, hot sauce, garlic powder, cayenne if using, salt, and pepper. Stir until well combined.
04 - Add grated cheddar cheese one handful at a time, whisking until completely smooth and melted before adding more cheese.
05 - Once all cheese is incorporated and sauce is velvety smooth, taste and adjust seasonings as desired. Serve immediately while hot.