1. In a medium bowl, whisk yolks and sugar until thick and pale, about 1 minute. Whisk in flour and cornstarch until fully blended and thick.
2. In a medium saucepan, bring milk to a boil over medium-high heat. Very carefully, pour a little hot milk into yolk mixture while whisking constantly. Keep whisking yolk mixture while slowly adding about half the milk. (This tempers the egg yolks slowly so they won't curdle.) Pour yolk mixture into saucepan with the rest of the milk and, while whisking constantly over medium heat, cook custard for 1 to 3 minutes or until it thickens. (Make sure to whisk all around the inside edge of the pan.) Whisk in vanilla.
3. Pour custard into a shallow bowl. Press plastic wrap directly onto surface of custard so it doesn't form a skin while you prepare the crust. At this point, custard may be refrigerated for up to 2 days.
4. Make the pastry tart shells. Preheat oven to 400 degrees F. Unfold 1 pastry sheet on a lightly floured surface. (Keep the second pastry sheet in the refrigerator.) Roll out sheet to a 12-inch square. Cut into four 6-inch squares. If desired, trim edges to make a circular shape. Place pastry squares on an ungreased baking sheet. Using your finger or a pastry brush, lightly wet edge of each pastry square with water. Fold over edges 1/2 inch on all sides, pressing firmly to form a rim. Prick center of pastry all over with a fork.
5. Bake for 13 to 15 minutes or until pastry is golden and puffed. Let cool 1 minute, then gently press down on the puffed centers of the shells with the back of a spoon to create a shallow well for the custard. Cool on a wire rack. Repeat with second pastry sheet, to make a total of 8 tart shells.
6. Prepare the clementines. Peel and separate segments.
7. Assemble the tarts. Divide custard evenly among the 8 tart shells. Arrange clementine slices decoratively on top of custard. Sift confectioners' sugar over clementines on each tart.
8. Place an oven rack about 8 inches below the broiler element and turn on broiler. Working in two batches, place tarts on a baking sheet and broil until pastry is golden and custard and clementine slices are warm, about 11/2 to 2 minutes. Be careful not to burn the pastry. Serve immediately.
Source: Hannaford fresh Magazine, January - February 2015