1) Custard: whip the egg yolks with the sugar and vanilla essence, then mix in the flour. Continuing to mix, gradually add in the hot milk. Place the custard on a moderate heat and thicken, mixing continuously. Transfer the custard to a bowl, cover with clingfilm and leave to cool in the fridge, but do not solidify.
2) Filling: bring the cream and the liqueur to the boil, then pour it onto the chopped chocolate. Mix and leave the filling, which must remain fluid, to cool.
3) Blind baking: roll out the shortcrust pastry to a thickness of 3-4 mm and cover the greased and floured mould. Trim the edges of the pastry and press it onto the base. Cover the shortcrust pastry with a disc of greaseproof paper and fill the mould with rice. Bake at 175° for 15 minutes. Take out of the oven, remove the paper and the rice and continue the cooking for a further 4-5 minutes in a static oven with heat underneath only. Take out of the oven and turn out the baked shortcrust pastry onto the grid.
4) Cover the base of the tart with 3 spoonfuls of filling, distribute the 8 Pastefrolle Balocco, coarsely crushed, and pour on the remaining filling. Place the tart in the fridge for 30 minutes, then pour on the custard, levelling it off.
5) Decoration: before serving, keep the tart at room temperature for 15/20 minutes. Brush a couple of grapes with the apricot gelatin and dip them in the caster sugar. Decorate the centre of the tart with the grapes, frosted and unfrosted, and the Pastefrolle Balocco.
An extra tip:
The frosting exercise allows shiny and very tempting fruits to be obtained. A mouth-watering alternative is to frost the grapes with a covering of melted dark chocolate.