Created by ellie on February 15, 2016
Step 1: Preheat oven to 350 degrees F.
Step 2: Spray a 9 inch baking pan with nonstick spray
Step 3: Cook macaroni according to package directions; drain.
Step 4: Meanwhile in a large saucepan over medium heat melt the butter; add onion, stirring until softened (5 minutes). Stir in flour and cook stirring for another minute; gradually whisk in milk until mixture is smooth; cook; stirring constantly until sauce bubbles and thickens (under 5 minutes). Stir in cheese, salt, mustard and pepper; cook stirring until cheese melts - another minute or so. Remove from heat and stir in macaroni.
Step 5: Spoon mixture into prepared pan and sprinkle bread crumbs over mixture. Spray crumbs with non-stick cooking spray.
Step 6: Bake for 30 minutes or until casserole is bubbly and top is golden.