Pastry: In large bowl, stir together flour, sugar, rind and salt. Cut in butter and shortening until mixture resembles coarse crumbs. Stir together egg yolk and water; gradually pour into dry ingredients, stirring briskly. Add more water if necessary to form dough that holds together. Press into ball and flatten slightly. (Dough can be wrapped and chilled for up to 3 days. Bring to room temperature before continuing with recipe.).
On lightly floured pastry cloth and using stockinette-covered rolling pin, roll out dough to slightly less than 1/4-inch (5 mm) thickness. Cut out sixteen 3-1/2-inch (9 cm) rounds. Ease into muffin tins, allowing 1/2 inch (1 cm) to come up sides. Prick bottom and sides. (Shells can be wrapped and refrigerated for up to 1 day.) Bake in 400°F (200°C) oven for 8 to 10 minutes or until golden. Remove from tins; let cool on racks.
Clementine Pastry Cream: Meanwhile, in heavy saucepan, whisk together egg yolks, milk, sugar and salt. Blend in flour and bring to simmer over medium heat, whisking constantiv, until thickened and smooth. Blend in clementine juice and rind; reduce heat to low and simmer gently, whisking constantly, for 3 minutes. Remove from heat and stir in butter, liqueur and vanilla.
Transfer to heatproof bowl and cover surface with buttered waxed paper; refrigerate until chilled, about I hour, or up to 1 day.
Topping and Glaze: Spoon cream into pastry shells. Refrigerate for up to 2 hours. Peel clementines; with sharp knife, remove thin outer membrane and cut out segments. Transfer to sieve and let drain until serving time. Pat dry and divide among tarts. Heat marmalade until melted; strain and brush lightly over tarts.