1. Heat oven to 325 degrees. Place cookies in the bowl of food processor; pulse until fairly fine, yielding 1 cup crumbs. Transfer to a medium bowl, and stir in 4 tablespoons melted butter. Press mixture into bottom and sides of a 9-inch pie tin. Bake until set and slightly darkened, 12 to 15 minutes. Do not overbake. Set aside.

2. Turn oven up to 375 degrees. Fill a small saucepan with water. Add potato, bring to a boil, reduce heat, and simmer until potato is very tender, about 12 minutes. Drain.

3. In a bowl, combine flour, salt, ginger, cinnamon, nutmeg, and cloves; set aside.

4. Pass potato through a food mill or potato ricer into the bowl of an electric mixer. Add sugar, eggs, and condensed milk. Mix until combined. Stir in remaining 3 tablespoons butter until combined. Add reserved flour mixture, and combine. Pour filling into cooled crust, and bake until filling is set, 30 to 35 minutes. Serve at room temperature with whipped cream, if desired.