Preheat oven to 400 degrees.
Add olive oil to large pot of boiling salted water.
Add pasta to boiling water, and cook pasta to the directions on the package. It is best to cook the pasta al dente, which means taking a minute or two off the cooking time. Drain well.
Meanwhile the pasta is boiling, heat milk in a saucepan on low heat.
At the same time, in a large pan, melt 6 tablespoons of butter on low heat.
When butter is melted, add a spoon full of flour at a time, and whisk until all flour has been added and all clumps are gone.
While still whisking, add the hot milk, and cook until the mixture is thickened and smooth.
Remove mixture off heat, and add Gruyere and white cheddar a little at a time, while mixing to avoid clumps.
Add salt, pepper and nutmeg to the sauce mixture.
Add the cooked pasta, and stir well. Place mixture in baking dish.
Melt the 2 remaining tablespoons of butter, and combine them with the italian breadcrumbs. Sprinkle breadcrumbs on top of dish.
Bake for 30 minutes, or until the sauce is bubbly and breadcrumbs are browned on the top.