1. In a 350° oven, bake pecans in an 8- or 9-inch-wide pan, shaking often, until lightly toasted, about 10 minutes. Pour from pan. When cool, whirl in a blender or food processor until finely ground.
2. Brush interiors of 10 tart pans (4 1/2 in. wide with removable rims; see notes) with the melted butter. Sprinkle 2 tablespoons ground toasted pecans over bottom of each pan. Set pans slightly apart on 2 baking sheets (14 by 17 in.).
3. In a bowl, with a mixer on medium-high speed, beat cream cheese to blend with 2/3 cup sugar, 2 tablespoons brandy, and 2 tablespoons maple syrup. Add eggs, pumpkin, cream, cinnamon, ground ginger, and nutmeg; stir to mix, then beat until well blended. Fill tart pans equally with cheesecake mixture.
4. Bake in a 325° oven until centers no longer jiggle when pans are gently shaken, 20 to 25 minutes.
5. Meanwhile, in a small bowl, mix remaining 1/2 cup chopped pecans and the crystallized ginger.
6. In another bowl, mix sour cream with remaining 2 tablespoons sugar, 1 tablespoon brandy, and 1 tablespoon maple syrup. Spoon mixture equally onto cheesecakes and spread level. Sprinkle pecan-ginger mixture equally over sour cream topping.
7. Return tarts to oven and bake to firm sour cream topping slightly, about 10 minutes. Transfer to a rack and let cool at least 30 minutes. Serve warm, or cover airtight without touching tops, and chill until cold, at least 2 hours or up to 1 day. To serve, remove pan rims and set cheesecakes on plates.