On lightly floured surface, with floured rolling pin, roll disk into 12-inch round. Gently roll dough around rolling pin to transfer to 9-inch tart pan with removable bottom. Gently press dough onto bottom and side of pan. Run rolling pin along top of tart pan to trim away excess dough. Freeze 30 minutes or until very firm.
With fork, pierce dough all over. Line tart shell with foil and fill with pie weights or dry beans. Bake 15 minutes. Reduce oven temperature to 350 degrees F. Remove foil and weights. Bake crust another 15 to 20 minutes or until golden. Cover rim with foil if browning too quickly. Cool in pan on wire rack.
While crust cools, in 2-quart saucepan, heat 3/4 cup milk to simmering on medium. In heatproof medium bowl, whisk together egg yolks, 6 tablespoons milk, and sugar until blended; whisk in cornstarch and flour until smooth. Slowly whisk hot milk into egg mixture. Return to same saucepan.
Cook mixture on medium 4 minutes or until very thick, whisking constantly. Remove from heat. Whisk in and salt until smooth. With knife, cut vanilla bean lengthwise in half; scrape out seeds and whisk into milk mixture.
Transfer mixture to small bowl. Cover surface directly with plastic wrap. Refrigerate until cool, about 45 minutes. (Can be refrigerated up to 1 day; remove from refrigerator 30 minutes before using.).
Peel oranges and thinly slice crosswise.
Spread pastry cream evenly in cooled tart shell.
Arrange orange slices in one layer on pastry cream, overlapping slightly. Can be refrigerated, covered, up to 2 hours.
To serve, in 1-quart saucepan, combine jelly and Triple Sec. Heat on medium until melted, whisking. Cool slightly and brush fruit with jelly. Garnish with currants.