Preheat your oven to 350F/180C.
Slice the top rind off your brie and lay sliced garlic and rosemary leaves directly on it and sprinkle with a little bit of olive oil.
Put it in a small baking dish and bake it in the oven for 15 minutes.
Meanwhile, cook pasta in a large pot of salted water according to the package direction, in the last minute of cooking add the spinach to the pot, then drain both pasta and spinach. Reserve ¼ cup water you cooked pasta in.
Return pasta and spinach back to the pot and gently mix everything with 4 tbsp. of grated parmesan cheese, 2 tbsp. of olive oil and salt and pepper, add a few splashes (¼ cup) of reserved water to make it a bit runny. Cover with a lid and set aside.
When brie is completely melted pour it in the pasta with a bit more water if the sauce gets too think to stir. You want pasta to be fluid not solid.
Empty the pasta into a buttered baking dish and sprinkle with grated mozzarella. Bake at 350F for 20 minutes until mac 'n cheese is heated through and forms golden crust on top.