TOTAL TIME 1 hour 35 minutes
3 tablespoons butter, more for greasing pie plate
4 cloves garlic, minced
1 medium leek, white and light green parts only, minced
4 small cipollini onions, minced
1 tablespoons minced Rosemary
3 cups heavy cream
2 pounds (about 6 medium) Keuka Gold potatoes (unpeeled), sliced 1/8-inch thick
ground white pepper
Preheat oven to 350 degrees. Butter a 9-inch deep-dish glass pie plate.
In a wide saucepan, combine 3 tablespoons butter, garlic, leek and onions. Place over medium-low heat and sauté until mixture is light golden, about 15 minutes. Add 2 tablespoons tarragon, the cream and potatoes, and mix well. Simmer gently until potatoes are barely tender, about 15 minutes. Season with salt and white pepper to taste.
Using a slotted spoon, transfer potatoes to pie plate, spreading them evenly and pressing lightly to compact them. Drizzle with 2 to 3 tablespoons of cream from pan. Cover with foil and bake for 40 minutes. Remove foil and continue to bake until top is light golden brown, about 10 more minutes. Remove from heat and allow to rest for 15 minutes. Garnish with a sprinkling of chopped tarragon, and serve.