Wash the orange, rub dry, rub half of the peel. Put flour, oat flakes, 250 g sugar, allspice, cinnamon, orange peel and butter in flakes into a mixing bowl and knead into crumbles using the dough hooks of the hand mixer.
Press half of the crumbles onto a greased fat pan of the oven (31 x 39 cm) as a base.
Roughly chop the chocolate and dissolve in 120 ml hot espresso. Separate the eggs. Beat the egg whites and salt with the whisk of the hand mixer until stiff, slowly adding 150 g sugar. Mix egg yolks, almond paste and cloves.
Stir in the chocolate espresso mixture. Carefully stir in the beaten egg white and buckwheat flour alternately. Smooth the mixture on the crumble base and spread the remaining crumbles on top. In the preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: see
manufacturer) bake for approx. 25 minutes, take out and let cool on a cake rack.
Bring 60 ml espresso, icing sugar and coffee liqueur to the boil in a small pot. Let it boil down at medium heat to a syrup. Use a spoon to spread the syrup over the cake and cut it into pieces (approx. 5 x 5.5 cm).