Gather ingredients: 2 cups shredded cheddar cheese, 1 cup shredded Monterey Jack (optional), 2 tbsp butter, 2 tbsp all-purpose flour, 2 cups milk (or 1 1/2 cups milk + 1/2 cup half-and-half), 1/2 tsp salt, 1/4 tsp black pepper, 1/2 tsp garlic powder (optional), 1/4 tsp paprika (optional), 1/4 tsp cayenne (optional)
Melt butter in a saucepan over medium heat
Whisk in flour and cook 1–2 minutes, until smooth and lightly golden
Slowly whisk in milk until the mixture is smooth and thickened, about 3–5 minutes
Reduce heat to low
Add cheese a handful at a time, stirring until melted and smooth
Season with salt, pepper, and optional spices
If too thick, whisk in a splash of milk until desired consistency
If too thin, simmer on low while stirring until it thickens
Serve immediately over chips, nachos, or roasted potatoes
Keep warm on low heat, stirring occasionally, and re-thin with a little milk if needed