Baked Ritz Mac & Cheese

1 lb shells, cooked al dente
1 lb mild Cheddar Cheese
1/2 lb Monterey Jack Cheese
1/4 cup Parmesan and Roman Cheese blend
3 cups half and half
2 Tbs butter
1/2 cup sour cream
1/2 tsp chicken base (paste)
1 sleeve Ritz Crackers, crushed
ground pepper, to taste

Preheat oven to 350 degrees.  Heat water for pasta, cook to al dente then drain.  In medium size saucepan add cheeses, half and half, butter, sour cream and chicken base.  Simmer on low until all cheeses are melted, stirring.  Add pasta to cheese, mix then add to baking dish ( I use approx 9 x 13).  Add crackers crumbs to top.  Bake until starts to brown on top. (approx. 30 mins.)