Preheat oven to 375°F. In a small pot, add the butter and melt. When melted, add the flour and stir for 1-2 minutes.
Add the milk, salt, and nutmeg, and whisk together until flour mixture (roux) is dissolved. Simmer until thick enough to coat the back of a spoon and place to one side. You just made a bechamel!
Place meatballs on an aluminum foil-lined baking sheet and cook in oven until lightly brown, approximately 20 minutes.
While meatballs are cooking, in a large pot, bring water to a boil and cook the pasta according to product instructions. Strain and set aside to cool.
In a large bowl, beat the eggs. Add the peas, tomatoes, basil, parmesan, mozzarella, pepper, bechamel, meatballs (and their drippings) and pasta. Mix all together and place in a pre-greased 9″x13″ glass baking dish.
Bake in oven for 45 minutes to one hour, until golden brown. If desired, turn broiler on low to further crisp the top of the bake before taking out of the oven, approximately one minute.
Take out and serve immediately. Buon appetito!