Melt the butter in a large pan over medium heat. Add the garlic and cook until aromatic, about 1 minute. Add the shrimp and scallops and cook for 3 minutes, or until cooked through (the shrimp will be pink). Do not overcook or the shrimp and scallops will become rubbery.
Remove the shrimp and scallops from the pan and set aside.
To the pan, add the heavy whipping cream, parmesean, salt, and pepper. Continue to cook over medium heat until the sauce has thickened, about 10-15 minutes. Stir frequently to avoid burning.
While the sauce is cooking, fill a large pot with lightly salted water. Bring to a boil, and add in the pasta. Cook until al dente (firm to the bite), about 8 minutes. After cooking, keep the pasta in the water to avoid it drying out.
Once the sauce has thickened, add the drained fettuccini, shrimp, and scallops all to the pan and stir to combine.
Serve and enjoy, adventurer!