2 tbsp butter
2 tbsp all-purpose flour
1 cup milk
1-1/2 cups shredded cheddar cheese
salt and pepper to taste
Melt butter in a saucepan over medium heat; whisk flour into butter until smooth. Pour milk into butter mixture and stir with a wooden spoon to combine. Cook and stir until mixture thickens, about 3 minutes. Add cheese and stir until cheese is melted, about 3 minutes more. Season with salt and pepper.