In large pot of salted water, cook pasta until el dente. Drain and set aside.
In a large pot, melt butter and add flour to make a rue. Cook until brown.
Add pepper and dry mustard.
Add cream and whisk until well incorporated with rue. Continue whisking and add in the milk. Whisk until milk thickens.
Take off of heat and add in cheese. Mix until cheese melts through.
Add cayenne pepper and vegeta. Season to taste.
Mix in cooked pasta. Transfer to a casserole dish that has been sprayed with cooking spray.
Top with crushed saltines and a handful of cheese.
Cook for 30 min covered in a preheated oven at 350 degrees. Uncover and cook 10-15 more minutes until golden and cheese it melted.