Rich and Creamy Smoked Cheddar Sauce

This is a take on my typical cheese sauce, and one that I laid out in a comment on one of the posts, but it's so good it deserves it's own entry.  This is one of those things that's so easy and yet so good that you'll find yourself thinking "I'm a freaking wizard!".  Mac and cheese is an obvious usage, but it's good on baked potatoes, eggs, hash browns, or wherever else you want cheesy goodness.  Just remember that the final sauce is only as good as the cheese you start with.

2 1/2 C whole milk
22 g sodium citrate*
 2 small onions, chopped
 6 cloves garlic, chopped
 2 T butter or bacon grease
 2 T dijon mustard, or to taste
salt and pepper to taste
8 oz sharp cheddar cheese, grated
8 oz smoked cheddar cheese, grated
Cayenne to taste

Saute the onion and garlic in the butter/grease until translucent.  Add the milk and sodium citrate and bring to a simmer.  Add the cheese, a handful at a time, allowing it to melt in while stirring frequently.  Blend the cheese sauce either in a blender or with an immersion blender.  Add the mustard, cayenne, salt, and pepper.  Adjust seasoning as necessary.

*Note: a lot of the cheddar you'll find out there is actually labeled as "cheese product".  Check the label; if it contains sodium phosphate you probably don't need the sodium citrate (they both emulsify the sauce and keep the fats and liquids from separating).