Let tofu and feta cheese stand at room temperature while preparing the potatoes. Quarter potatoes. In a large saucepan cook potatoes and garlic, covered, in lightly salted boiling water for 20 to 25 minutes or until tender.
Meanwhile, place tofu in a blender container or food processor bowl. Cover and blend or process until smooth. Set aside.
Drain potatoes and garlic; transfer to a large bowl. Mash potatoes and garlic with a potato masher or beat with an electric mixer on low speed. Stir in pureed tofu, olive oil, salt, and pepper. If needed, add milk, one tablespoon at a time, until potatoes are light and fluffy. Stir in feta and Parmesan cheeses. Makes 6 servings.