In large bowl, whisk flour wit salt. Using pastry blender or 2 knives, cut in butter and lard until mixture resembles coarse crumbs with a few larger pieces.
In separate bowl, whisk together egg yolk, ice water and sour cream; drizzle over flour mixture, tossing with fork to form ragged dough and adding up to 1 tsp more ice water if necessary. Shape into disc; wrap in plastic wrap. Refrigerate until chilled, about 1 hour. (Make-ahead: Refrigerate for up to days or freeze for up to 1 month.)
On lightly floured work surface, roll out dough to generous 1/8-inch (3 mm) thickness. Using 3 3/4-inch (10 cm) round cutter, cut out 12 rounds, rerolling scraps as necessary. Press 1 round into each well of 12-count muffin pan. Refrigerate until chilled, about 30 minutes.
While dough is chilling, in bowl, beat together pumpkin, cream, brown sugar, eggs, cinnamon, ginger, vanilla, cloves, nutmeg and salt. Divide among pastry shells.
Bake in 350°F (180°C) oven until filling is set and slightly puffed, about 30 minutes. Let cool completely in pan. Refrigerate until chilled, about 1 hour. Remove from pan. (Make-ahead: Refrigerate in airtight container for up to 24 hours.)
In bowl, beat cream with icing sugar until stiff peaks form; spoon 4 tsp onto
each tart. Sprinkle with nutmeg.
Tip from The Test Kitchen: This recipe uses all but a small amount of one can of pumpkin purée. Use the leftovers to make our No-Bake Pumpkin Cheesecakes for Two.