Cook the elbow macaroni according to package instructions, then drain and set aside.
In a saucepan, melt the butter over medium heat.
Add the evaporated milk, Velveeta cheese, and shredded cheddar cheese to the saucepan. Stir until the cheeses are melted and the mixture is smooth.
In a greased crock pot, layer the cooked macaroni and cheese sauce, seasoning each layer with salt and pepper.
Cover and cook on low for 2-3 hours, stirring occasionally.
For the spicy version, add the evaporated milk, Velveeta cheese, shredded pepper jack cheese, and diced green chilies to the saucepan. Stir until the cheeses are melted and the mixture is smooth.
In a greased crock pot, layer the cooked macaroni and cheese sauce, seasoning each layer with salt, pepper, and hot sauce.
Cover and cook on low for 2-3 hours, stirring occasionally.