In food processor bowl, combine flour, sugar, salt and butter; pulse until fine crumbs form. Add egg and quickly pulse to combine.
On lightly floured surface, turn out dough and gently form into ball. Wrap dough in plastic wrap and refrigerate until needed.
For the pastry cream:
In mixing bowl, whisk together egg yolks and sugar until pale yellow. Whisk in flour until just incorporated.
In small saucepan, bring milk, cream and vanilla to simmer over high heat. Gently blend cream mixture into yolk mixture, then return to saucepan and whisk continuously over medium-high heat until bubbling and thickened, 3–5 minutes. Pour pastry cream into small bowl, cover surface with plastic wrap and cool to room temperature.
On lightly floured surface, roll out dough to 1/4-inch thickness. Cut out six 7-inch-diameter rounds and press rounds into six 5-inch-diameter fluted tart tins, trimming edges. Refrigerate for 30 minutes.
Preheat oven to 350 degrees F. Line each tart crust with foil and fill with pie weights, dry rice or dry beans. Blind bake crusts until just dried, 10–12 minutes. Remove weights and foil, and bake another 5–7 minutes until fully baked and crisp. Cool to room temperature.
Divide pastry cream filling among tart crusts and top with berries, petals or flowers and dusting of icing sugar.