Mix flour, cocoa powder, almonds and icing sugar. Add 100 g butter in pieces and egg yolk, knead to a dough. Wrap dough in foil and chill for at least 1 hour
Roll out the dough thinly on a floured work surface. Cut out 6 circles (each approx. 12 cm Ø). Grease 6 Tartelettes (each approx. 10 cm Ø), dust with flour and line with dough circles. Place baking paper on top and fill peas into the trays. Bake on the lower shelf in a preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: see manufacturer) for approx. 15 minutes. Remove paper and peas. Continue baking for about 5 minutes. Take out and cool lukewarm on a cake rack
Wash the lemons hot and grate them dry. Grate the zest of 1 lemon thinly. Halve the grated lemon and another lemon, squeeze the juice. Heat lemon juice and zest, 75 g butter and sugar in a saucepan until the butter has melted
Mix eggs and starch. Stir in 3 tablespoons of the lemon cream, stir back into the pot. Let simmer for about 1 minute while stirring. Pass the cream through a sieve and spread it on the lukewarm tartelettes. Leave to cool
Cut 6 thin slices from the middle of the last lemon. Decorate each tartlet with 1 slice of lemon and leave to cool
waiting time approx. 1 1/2 hours