Preheat oven to 325 degrees F. In a bowl stir together flour, ground sage, and the 1/4 teaspoon salt. Cut in shortening until pieces are the size of small peas. Sprinkle 2 tablespoons of the cold water over part of mixture; gently toss with a fork. Push to side of bowl. Repeat with remaining cold water, 1 tablespoon at a time, until all is moistened. Shape into a ball.
On a lightly floured surface roll pastry 1/8 inch thick. Cut circles with a 3- or 3-1/2-inch round cutter (depending on size of tart or individual brioche pans used); reroll pastry as necessary. Line 2-1/2- to 3-inch round fluted tartlet pans or individual brioche pans with the pastry circles. Trim off any excess dough. (If desired, cut leaf-shape pieces from pastry scraps for garnish. Brush with mixture of 1 egg white and 1 tablespoon water. Place on a baking sheet; bake for 10 to 12 minutes.)
Place pans in a 15x10x1-inch baking pan for easier handling. Set aside.
For filling, in a small skillet cook sausage and onion until sausage is lightly browned and crumbly, breaking up sausage into fine pieces as it cooks. Drain on paper towels. Set aside. Stir together eggs, pumpkin, milk, sugar, salt, and cinnamon. Stir in sausage mixture. Spoon a slightly rounded tablespoon of mixture into each pastry-lined pan. Bake for 15 to 20 minutes or until filling is set.
Remove tarts from oven and let cool in pans 10 to 15 minutes or until firm. Carefully loosen with a wooden toothpick; remove from pans. Cool on wire racks. Wrap and chill at least 2 hours or up to 24 hours.
To serve, place tartlets on baking sheet. Reheat in a 350 degree F oven for 8 to 10 minutes or until heated through. If desired, place sage leaves or baked pastry leaves on top of each tart. Makes 24 to 30 appetizer tarts.