Bring a large pot of salted water to a boil and cook the macaroni pasta until it’s al dente. Immediately take off the water and reserve.
In a large sized bowl whip the egg until there are no strings of white or yolk left. Add the heavy cream, milk, 2 oz Parmesan, Gruyere, black pepper, salmon and 1 teaspoon of salt. Mix until combined. Add the pasta and incorporate everything together.
Transfer Mac and cheese to a 2 quarts baking dish.
Mix the remaining Parmesan with the panko breadcrumbs and top Mac and cheese with it.
Bake for 20 minutes. Turn up the broiler for the last 3 minutes to brown the top.