For the perfect pie crust, you'll need: 8 tablespoons butter (1 stick) 6 tablespoons shortening 2 1/2 cups all purpose flour 2 teaspoons salt 4 teaspoons sugar 6 to 8 tablespoons ice water Sweet tips: This recipe makes enough dough for 12 mini pies and pie toppers. Leftover dough can be double wrapped in plastic wrap and refrigerated for 1 week, or frozen for up to 3 weeks.
Chop the butter and shortening into 1/4-inch pieces. Place in the freezer to chill while you prepare the other ingredients. Blend the flour, salt, and sugar in a food processor. Add the chilled shortening and process until the mixture climbs the walls of the processor bowl. Add the butter, one piece at a time, and process thoroughly.
Add the ice water 1 tablespoon at a time until the mixture comes together in a ball and makes 2 laps around the processor bowl. Remove the dough, divide it in half, and flatten each half into a disc. Wrap each disc in plastic wrap and chill in the refrigerator for 30 minutes.
Pie Filling Combine the cream, rosemary, cinnamon, cayenne, salt, nutmeg, and brown sugar in a saucepan over low heat; bring to a boil, stirring gently. Let cool, then chill in the refrigerator in an airtight container for 2 hours. Preheat the oven to 350°F. Generously grease a 12-cup muffin tin with butter or cooking spray.
On a thoroughly floured surface, roll out the crust to a thickness of 3∕16 inch. Using a 4-inch diameter round cutter, cut 12 crusts. Re-form and re-roll the dough as necessary, keeping plenty of flour on your work surface. For this pie, you want the crusts to be slightly larger than normal. Cut them out as usual, then (working on the floured surface) tap around the edges of each crust with the heel of your hand to stretch it slightly.
Carefully shape the crusts into the wells of the muffin tin, crimping the edges with your fingers and folding them out over the top of the pan. This will help prevent the crusts from shrinking while they bake. Pierce the bottom of each mini crust with a fork. Bake for 12 minutes, until lightly browned.
Strain the chilled cream mixture and discard the solids, making sure to squeeze all the liquid out first.
Lightly beat the egg, then stir together with the cream mixture, sweet potato purée, and vanilla. Fill each mini crust with 2 tablespoons of filling.
Bake for 30 minutes, until the crust is lightly browned. Allow to cool in the muffin tin for a few minutes, then carefully remove the pies from the pan and place on a wire rack to finish cooling. To remove, first try to spin the pies in the muffin wells. If they need a little extra help, run a butter knife along the edge of the crusts to pop them out of the tin.
Serve, or refrigerate in an airtight container for up to 2 days.