Heat oven to 375 degrees F.Cook macaroni in a large pot of salted boiling water until tender but not mushy, about 8-10 minutes. Drain well and pour into a large mixing bowl.
Melt on low the Velvetta Cheese and ¾ cup milk until melted (stir often)Pour Melted Cheese Sauce over Pasta and Stir. Add in butter, ¾ cups milk, eggs, 1 cup shredded cheeses, salt and pepper. Mix well and transfer to a 2 quart baking dish. Pour the remaining cheese on top.
Bake until top crust is golden brown and casserole is bubbling, about 25 minutes. Serve hot .