1. Cook the fettuccine pasta according to package instructions until al dente, then drain and set aside.

2. In your slow cooker, add the heavy cream, grated Parmesan cheese, and unsalted butter.

3. Set the slow cooker to low and stir occasionally until the butter is melted and the mixture is smooth and creamy, about 1 to 1.5 hours.

4. Once the sauce is ready, add the cooked fettuccine to the slow cooker and toss to coat the pasta evenly.