Sharp Cheddar Shells and Cheese
Bring a large pot of salted water to a boil. Add shells; cook about 8 minutes, following package directions. Drain.Advertisement
Meanwhile, melt butter in a medium saucepan over medium heat. Add onion and cook 5 minutes. Whisk in flour. While whisking, add milk in a thin stream. Whisk in mustard powder, salt and pepper.
Bring to a simmer, whisking occasionally. Simmer 3 minutes. Remove from heat and whisk in cheese. Top with crushed pretzels.