Grease a tart mould with a removable base (24 cm Ø) and dust with flour. Quickly knead 150 g flour, ground almonds, 50 g sugar, 100 g butter in pieces and egg to a smooth shortcrust pastry.
Roll out to a circle (approx. 28 cm Ø) on a lightly floured piece of baking paper. Line a baking tin with the circle, pressing the dough up at the edges. Prick the base several times with a fork and chill for about 30 minutes.
Preheat oven (electric cooker: 175 °C/circulating air: 150 °C/gas: see manufacturer). Sprinkle the base with chopped almonds. Bake the tart in the hot oven on the lowest shelf for about 20 minutes. Remove from the oven, allow to cool, then remove from the mould.
Stir the starch and 6 tablespoons of nectar until smooth. Boil up the rest of the nectar and 2 tablespoons of sugar. Stir in the starch and simmer for at least 1 minute while stirring. Leave to cool. Wash strawberries, clean all but 1 for decoration and cut into small pieces.
Mix with the thickened juice, pour onto the tart and chill for about 3 hours.
Chopping chocolate. Melt in 50 g cream and 1 teaspoon butter over low heat. Let the sauce cool down for about 5 minutes.
Whip the sour cream and vanilla sugar with the whisks of the mixer for about 2 minutes. Whip 250 g cream until stiff, fold in. Pour cream as a large tuff onto the tart. Decorate with the rest of the strawberry and drizzle with chocolate sauce.