Preheat the oven to 350F/180C. Lightly butter a deep 2 1/2-quart/2L casserole.

Bring the large pot of salted water to a boil over high heat. Add the oil, then the elbow macaroni, and cook until the macaroni is just tender, about 7 minutes. Do not overcook. Drain well. Return to the cooking pot.

In a small saucepan, melt eight tablespoons of the butter. Stir into the macaroni. In a large bowl, mix the Muenster, mild and sharp Cheddar, and Monterey Jack cheeses. To the macaroni, add the half-and-half, 1 1/2 cups of the shredded cheese, the cubed Velveeta, and the eggs. Season with salt and pepper. Transfer to the buttered casserole. Sprinkle with the remaining 1/2 cup of shredded cheese and dot with the remaining one tablespoon of butter. Sprinkle with bread crumbs if using.

Bake until it's bubbling around the edges, about 35 minutes. Serve hot.