3 cups whole milk
1/2 cup unsalted butter
1/2 cup flour
2 tsp. kosher salt or 1 tsp.table salt
Heat milk in pot over medium heat til it just starts to bubble,but is not boiling, 3 to 4 minutes.
Heat butter over medium in separate pot. When butter has just melted, add flour and whisk constantly til mixture turns light brown. about 3 minutes. Remove from heat. Slowly pour warm milk, about 1 cup at a time, into butter flour mixture, whisking constantly. it will get very thick when you first add the milk and thinner as you slowly pour in the entire 3 cups. This is normal. Once all the milk has been added, set pot back over-medium high heat, and continue to whisk constantly. In the next 2 to 3 minutes, the sauce should come together and become silky and thick. use the spoon test to make sure it's read. To do this, dip a metal spoon into the sauce. If the sauce coats the spoon and doesn't slide off like milk, you'll know its ready. You should be able to run your finger along the spoon and have the impression remain. Add the salt.The mac sauce is ready to use at once and does not need to cool. Store it in the fridge for a day or two if you want to make it ahead of time. it will get a lot thicker when put in the fridge so it may need a little milk to thin it out a bit when it comes time to melt in the cheese. Try melting the cheese into the sauce first, and if it's too thick, then add milk as needed.