Cook potatoes, covered, in a small amount of boiling water about 25 minutes or until very tender. Drain; return to pan. Mash with a potato masher or beat with an electric mixer.
Meanwhile, in a food processor bowl, combine Parmesan cheese, butter, onions, and garlic. Process until mixture is combined and almost smooth. (Or beat with an electric mixer.)
Add cheese mixture to potatoes; add cream. Stir by hand or beat with an electric mixer on low speed until combined. Stir in salt and pepper. Makes 8 to 10 side-dish servings.