THE BEST homemade nacho cheese sauce! 2 Tbsp salted butter, 1 Tbsp flour, 1 cup milk, 1 1/4 cup shredded cheddar cheese, 1/2 cup salsa (chunky or smooth, your preference!) Melt butter over medium heat. Add flour and whisk until smooth. Gradually add milk, whisking after each addition. Continue whisking until milk mixture thickens, about 5 minutes. Remove from heat and stir in cheese until completely melted. Stir in salsa, and start dunking your chips! YUM!