Ingredients

• 1 lb medium boiling potatoes
• 1 tablespoon unsalted butter
• 1 whole large egg
• 1 large egg yolk
• 1 1/4 teaspoons salt
• 1/8 teaspoon black pepper
• 1/2 cup water
• 1 tablespoon unsalted butter
• 1/2 teaspoon salt
• 1/8 teaspoon black pepper
• 1/8 teaspoon freshly grated nutmeg
• 1/2 cup all-purpose flour
• 2 large eggs
• About 4 cups vegetable oil
• Special equipment: a potato ricer; a pastry bag fitted with a 1/2-inch star tip; a deep-fat thermometer

Instructions

1. Peel potatoes and cut into 1-inch pieces. Cover potatoes with cold salted water by 1 inch in a 2-quart pot, then simmer, uncovered, until tender, about 15 minutes.
2. Drain potatoes in a colander and return to pot. Dry potatoes by shaking pot over low heat until all moisture is evaporated and a film begins to appear on bottom of pot, about 2 minutes.
3. Force potatoes through ricer into a bowl. Add butter, whole egg and yolk, salt, and pepper and stir with a wooden spoon until very smooth. Keep potato mixture warm, covered.
4. Make pâte à choux: Bring water, butter, salt, pepper, and nutmeg to a boil in a 1-quart heavy saucepan over high heat, then reduce heat to moderate. Add flour all at once and stir briskly with a wooden spoon until mixture pulls away from side of pan, 1 to 2 minutes. Remove from heat and cool slightly, about 3 minutes. Add eggs 1 at a time, stirring well after each addition. Add potato mixture and stir until combined well. Transfer mixture to pastry bag.
5. Bring water, butter, salt, pepper, and nutmeg to a boil in a 1-quart heavy saucepan over high heat, then reduce heat to moderate.
6. Add flour all at once and stir briskly with a wooden spoon until mixture pulls away from side of pan, 1 to 2 minutes. Remove from heat and cool slightly, about 3 minutes. Add eggs 1 at a time, stirring well after each addition. Add potato mixture and stir until combined well. Transfer mixture to pastry bag.
7. Form and fry potatoes: Put oven rack in middle position and preheat oven to 200°F. Heat 2 inches oil in a 5- to 6-quart heavy pot over moderately high heat until thermometer registers 370°F. Resting metal tip of pastry bag on edge of pot, pipe 8 (2-inch) lengths of potato mixture directly into oil (use caution when piping into hot oil), using a small knife or kitchen shears to cut off each length of dough at tip of bag. Fry potatoes, turning over once with a slotted spoon, until crisp, golden, and cooked through, 2 to 3 minutes. Transfer to paper towels to drain briefly. Fry remaining potato mixture in batches in same manner. Transfer potatoes as fried and drained to a metal rack set in a large shallow baking pan in oven to keep them crisp and warm until ready to serve.
8. Put oven rack in middle position and preheat oven to 200°F.
9. Heat 2 inches oil in a 5- to 6-quart heavy pot over moderately high heat until thermometer registers 370°F.
10. Resting metal tip of pastry bag on edge of pot, pipe 8 (2-inch) lengths of potato mixture directly into oil (use caution when piping into hot oil), using a small knife or kitchen shears to cut off each length of dough at tip of bag. Fry potatoes, turning over once with a slotted spoon, until crisp, golden, and cooked through, 2 to 3 minutes. Transfer to paper towels to drain briefly. Fry remaining potato mixture in batches in same manner.
11. Transfer potatoes as fried and drained to a metal rack set in a large shallow baking pan in oven to keep them crisp and warm until ready to serve.