Pre-heat the oven to 375°F; butter a 2-quart baking dish.
Bring a large pot of heavily salted water to a boil; cook pasta to al dente; drain well.
Transfer hot pasta to a large bowl; toss immediately with Brie and cream cheese until melted and smooth.
In a separate bowl, whisk together eggs, mascarpone and parmigiano.
Stir egg mixture into pasta; season with pepper and nutmeg.
Turn pasta into prepared pan.
Place in the pre-heated oven and bake until golden brown and bubbling; about 30 minutes.
Remove from the oven and serve immediately.