Grease a springform pan (26 cm Ø). Knead flour, sugar, cocoa, 1 pinch of salt, butter in pieces, egg yolk and possibly about 1 teaspoon of ice-cold water first with the dough hooks of the mixer and then briefly with your hands until smooth.
Pour the dough into the mould and press it into the cake base. Chill for about 30 minutes. Bake in the preheated oven (electric cooker: 200 °C/circulating air: 175 °C/gas: see manufacturer) for 18-20 minutes. Leave to cool in the mould.
Remove from the mould and place a cake ring around it.
Break the chocolate into pieces, melt with 4 teaspoons of butter in a hot water bath. Sift the cocoa and cinnamon on top, stir in and leave to cool for about 10 minutes. Whip cream until stiff. Add the cooled but still liquid chocolate and fold in carefully and slowly with a dough scraper so that the cream remains nice and airy.
Spread on the cake base. Chill for about 4 hours.
For the compote, drain the cherries and collect the juice. Mix the starch with 3 tbsp. cherry juice. Boil up the rest of the cherry juice and sugar. Stir in the starch and simmer for about 1 minute while stirring. Fold in the cherries and let it cool down.
Remove the cake from the cake ring. Spread almost half of the stewed cherries on top. Add the rest of the compote.