Boil pasta in salted water according to box instructions and reserve 2-4 tablespoons of pasta water.
Carefully cut the top of the wheel of brie off, trying not to remove much of the cheese.
Use a spoon to scoop out all of the brie from inside the wheel, keeping the shape of the wheel intact.
To a large nonstick pan or pot over medium heat, add the brie cheese.
Slowly allow it to melt, then add heavy cream.
Make sure the heat is low enough that the sauce doesn't begin to bubble.
Then add the cheddar cheese.
Use a whisk to combine the cheeses with the cream and continue stirring until smooth.
Add seasonings and adjust to taste, but do not add chives yet.
To the pan/pot of cheese sauce, add the cooked and drained elbow pasta.
Gently stir to combine until all of the pasta is coated.
If necessary, add reserved pasta water to thin the sauce.
Serve mac and cheese in the scooped out brie rind OR simply serve in serving bowls.
Garnish with chives and enjoy while hot!