Step 1
Cook pasta following packet directions. Drain. Return to pan.
Step 2
Meanwhile, melt butter in a saucepan over medium-high heat. Add flour. Cook, stirring, for 1 minute or until bubbling. Gradually add milk and cream, stirring until smooth and combined. Cook, stirring, for 4 to 5 minutes until mixture boils and thickens. Add cheeses and mustard. Stir until melted and mixture is smooth.
Step 3
Add cheese mixture to pasta. Stir to combine. Stand for 5 minutes. Season with salt and pepper. Serve.