Quickly knead the flour, 100 g butter in pieces, salt, 1 tablespoon of sugar and 5 tablespoons of cold water into a smooth short pastry. Wrap dough in cling film and chill for about 1 hour. Roll out to a circle (28 cm Ø) on a floured work surface. Line a tart mould (24 cm Ø) with dough and chill for approx. 20 minutes. Line the tart with baking paper and fill in pulses.
Pre-bake in the preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: level 2) for approx. 20 minutes. Remove the legumes and baking paper and bake for another 10 minutes. Leave to cool on a rack. Coarsely chop the chocolate coating and melt over a warm water bath. Heat 300 g crème fraîche and 2 tablespoons of sugar. Beat 100 g butter in small pieces. Stir in milk and mix with chocolate coating. Pour immediately into the tart tin and chill for about 3 hours. Stir 300 g crème fraîche, 2 tablespoons of sugar and lemon zest until smooth. Select the berries and mix.
Stir in milk and mix with chocolate coating. Pour immediately into the tart tin and chill for about 3 hours. Stir 300 g crème fraîche, 2 tablespoons of sugar and lemon zest until smooth. Select the berries and mix. Remove the tart from the tin and cut into 16 pieces. Serve with crème fraîche and mixed berries. Decorate as you like with icing sugar and lemon balm