Bring a large pot of water to the boil and add rock salt. Preheat oven to 200°C.
COOK THE PASTA
Cook pasta 2 minutes less than instructions on the box.
MAKE THE SAUCE
Meanwhile, in another saucepan, heat milk and cream until it begins to simmer.
COMBINE
Mix corn starch with 2 tablespoon water to create a slurry. Add slurry to the cream mixture to thicken, then season with salt and pepper. Slowly add ¾ of the cheese into the sauce, whisking constantly, then add pasta to the mixture.
BAKE AND SERVE
Place the pasta in a greased baking dish. Bake in the pre-heated oven for approximately 15 minutes, or until bubbling and slightly caramelized on top.
