Adapted from The Peppermill, Brooklyn, NY
4 large russet potatoes
1 small onion, finely diced
2 tablespoons butter
8 ounces milk
5 ounces shredded Mozzarella cheese
2 tablespoons plus 3/4 teaspoon salt
Freshly ground pepper
1 1/2 cups flour
2 cups panko bread crumbs*
Canola oil for deep frying
For the dipping sauce:
4 ounces mayonnaise
1 tablespoon oil
Crushed red pepper
Peel and chunk potatoes; put in large pot and cover with water. Add 2 tablespoons salt and bring to a boil. Cook until potatoes are soft- about 15-20 minutes. Drain potatoes and return to pot over low heat. Cook until potatoes are dry. Transfer to a large bowl of mixer - fitted with whisk attachment.
Melt butter in a small skillet. Add onion and sauté until lightly golden. Add onions to potatoes and mix on low speed to break up potatoes. Add milk and cheese; beat on high until mixture is smooth and fluffy. Season with salt & pepper. Cover and refrigerate until very cold.
Scoop 1/3 cup of batter and roll into a 3" log. Dredge in flour, dip in eggs and coat with panko bread crumbs. Set aside on a tray and chill until cold. Repeat process with remaining batter.
Fill a deep skillet with at least 2" of oil. Heat oil to 350°F. Add croquettes and fry until golden on all sides and cooked through. Remove with slotted spoon and drain on a cooling rack or paper towels.
*Koshereye tip: Kikkoman brand panko crumbs are now certified kosher.