Preheat the oven to 400 degrees. Very lightly spray a 9-by-13 inch baking dish. Set aside.
Bring a large pot of salted water to a boil. Add 2-3 drops of olive oil to the boiling water. Add the macaroni, stir once and cook to al dente, about 2 minutes less than package directions.
Drain, rinse pasta and transfer back to pot. Melt 1 Tbsp of butter in the microwave. Pour over cooked pasta. Stir to incorporate the butter onto the pasta. Season pasta by adding salt, garlic salt and pepper. Set aside.
In a large saucepan, melt (not brown) remaining butter on medium-low heat. Once butter is melted, stir in flour, one tablespoon at a time. Stir mixture slowly but constantly with a wooden spoon, making sure the mixture does not have lumps. Reduce heat to low. Carefully add half and half and heavy cream. Stir occasionally, keeping a close eye on the mixture to avoid scorching. Allow mixture to slightly thicken. Once thickened, pour into the pot with pasta. Stir well until well incorporated.
Add 1 Cup Shredded Mild Cheese, ½ Cup Shredded Extra Sharp Cheddar Cheese, ½ Cup Shredded Mexican Cheese and ½ Cup Shredded Colby Jack Cheese. Add 2 Tbsp truffle oil. Stir well.
Transfer to the prepared dish. Top with remaining cheeses. Drizzle remaining truffle oil on top layer of cheese.
Bake until the top is lightly browned. Start checking at 12 minutes.
Let stand for 5-10 minutes before serving.