In a small saucepan melt the butter over medium heat until melted. Sprinkle in the flour and mix well until it bubbles and forms a smooth paste, about 1-2 minutes.
Slowly add in a little bit of the milk and whisk until no lumps are present. Keep adding a little bit of milk and whisking until combined until all milk is incorporated and the mixture thickens up. about 3-4 minutes.
Add in the grated cheddar cheese and stir until it is melted and combined about 3 more minutes.
Add salt and pepper to taste. Pour over your favorite steamed or roasted vegetables like asparagus, broccoli or cauliflower.