Combine flour and salt in a large bowl. Add butter and shortening; rub in with cold fingers until mixture resembles fine bread crumbs. Mix in sugar and orange zest thoroughly. Mix in vanilla extract. Stir in enough orange juice to bring dough together.
Knead dough briefly to form a smooth ball. Wrap in plastic wrap; refrigerate until firm, at least 1 hour.
Preheat oven to 350 degrees F (175 degrees C).
Roll dough out on a lightly floured work surface to a thickness of 1/8 inch. Cut out 12 circles using a 2 1/2-inch cutter and 12 circles using a 1-inch cutter.
Line 12 mini tart pans or a muffin tin with the 2 1/2-inch dough circles. Cover dough with about 1 tablespoon mincemeat filling. Lay 1-inch circles on top.
Bake in the preheated oven until tops are pale golden brown, 17 to 21 minutes. Cool slightly on wire racks, about 10 minutes. Dust with confectioners' sugar before serving.