Defrost the strawberries. For the dough, knead flour, 50 g icing sugar, 1 pinch of salt, 75 g cold butter in pieces and 2 tbsp. cold water to a smooth shortcrust pastry. Grease a square springform pan (24 x 24 cm; alternatively round, 26 cm Ø).
Press the dough with your hands to a flat bottom. Place the mould in a cool place for about 30 minutes.
Preheat oven (electric cooker: 175 °C/circulating air: 150 °C/gas: see manufacturer). Prick the dough in the mould more often with a fork. Pre-bake in the oven for about 20 minutes.
Puree the strawberries with lemon juice. Bring to the boil with sugar and 75 g butter while stirring. Mix starch with 7 tbsp. water until smooth, stir into the puree, simmer for about 1 minute. Remove from the stove. Mix egg yolk with 2 tbsp. hot cream, then stir the egg yolk mixture into the rest of the cream.
Spread on the floor.
Bake at the same temperature for about 20 minutes. Remove from the oven and leave to cool in the mould. Remove from the edge of the tin and cut into 40-50 squares (each approx. 3 x 3 cm). Dust with icing sugar.