Boil macaroni in large pot and drain excess water

While pasta draining, melt butter and add flour, mustard, and salt.

Add milk while whisking the mixture. Add in pre-melted velveeta cheese until heated through.

Remove from heat and add macaroni.

Spread in greased 1.5 quart shallow baking dish. Top with shredded cheese and bake for 20-25 minutes at 375 degrees F or until bubbly