Cook the pasta according to package directions 24 hours before needed. Boil in water for about 8 minutes. Drain and cool. Store in a resealable bag or container for 24 hours.
When ready to prepare, place the Velveeta and milk in a saucepan. Cook on medium-low until the cheese is melted and the mixture is smooth
Boil some water on the stove.
Remove the macaroni from the refrigerator and add the macaroni to the boiling hot water. Cook for 1 minute. Drain and set aside.
Spray a casserole dish with cooking spray.
Pour the elbows into the casserole dish. Set aside
In a saucepan, combine the sour cream, cream cheese and butter. Stir until cream cheese and butter are melted.
Pour the mixture over the hot pasta and stir until incorporated.
Pour the Velveeta mixture over the top of the pasta and stir until incorporated throughout.
Sprinkle the shredded cheddar cheese over the top.
Bake at 350 degrees for 20-25 minutes until the cheese is melted.
You can sprinkle some Keto breadcrumbs over the top for a little more crunch, but this is an optional ingredient.