Sort blackberries. Bring blackberries, 50 g sugar, cloves and 2 tablespoons water to the boil in a pot and pass through a sieve.
Mix butter and 80 g sugar. Stir in vanilla extract and double cream. Add flour, first with the dough hooks of the hand mixer, then knead with your hands to a smooth dough.
Roll out the dough on baking paper to a rectangle (approx. 20 x 30 cm). Spread the blackberry mixture on the dough, leaving an approx. 5 cm wide edge on one long side. Roll up the dough from the opposite side.
Wrap the dough roll in foil and chill for about 2 hours.
Cut the dough roll into approx. 0.5 cm thick slices and spread them on a baking tray lined with baking paper. Leave some space between the slices. In a preheated oven (electric cooker: 200 °C/ circulating air: 175 °C/ gas: see
manufacturer) bake for about 10 minutes. Remove and let cool on a cake rack.