Simmer the sauce gently to reduce excess liquid
Whisk in a small amount of cornstarch slurry
Add a roux made from butter and flour
Stir in more shredded cheese gradually
Use evaporated milk instead of regular milk
Add cream cheese for extra body
Mix in a little mashed potato or potato starch
Blend in a small amount of instant mashed potato flakes
Let the sauce rest off heat to thicken
Use less liquid when making the sauce
Add a pinch of xanthan gum
Incorporate a little sodium citrate for smoother emulsification