3 tablespoons butter
3 tablespoons all-purpose flour
1 cup milk
1 cup shredded cheddar cheese
salt, to taste
Melt butter in a saucepan over medium-low heat; add flour and whisk until smooth and bubbly. Remove from heat; gradually add milk, whisking to keep smooth. Return to heat and bring to a gentle boil, whisking constantly until thickened. Add cheese and stir until melted. Add salt.