In the bottom of the slow cooker, add the butter, cream cheese, heavy cream, and 4 cups of shredded cheese. Place the lid on top and turn on low.
Cook the gluten-free pasta 2 minutes less than the package directions. Drain.
Stir the cream mixture in the bottom of the slow cooker. Add the pasta to the slow cooker. Gently stir to avoid breaking up the noodles.
Place the lid on and continue cooking for 30 minutes.
Remove the lid and gently stir again
Cook for another hour. Stir.
Salt and pepper to taste.
Pour the remaining cup of shredded cheese over the top.
Cook and additional 10-15 minutes, until the cheese is melted.
Reduce heat to warm.
Serve.