Preheat oven to 180 degrees top/bottom heat (convection oven: 160 degrees). For the dough, separate the eggs. Beat egg whites with 50 g of the sugar until stiff. Set egg whites aside. Cream oil, egg yolks and remaining sugar. Add flour, baking powder and 125 ml of water.
Divide the dough in half. Add cocoa powder and milk to one half and mix with a whisk or pastry spatula. Divide the stiff egg whites in half, add one half to each of the two doughs and fold in with a pastry spatula.
Line a baking sheet (39 x 26 x 4 cm) with parchment paper and smooth the light batter onto it. Pour the dark batter in blobs on top and spread it as well. Drain the morello cherries in a sieve and press them into the dough. Bake cake in preheated oven for about 25 minutes. Let cool completely.
For the filling, boil milk with the pudding powder and sugar according to package directions. Pour pudding into a bowl and cover with plastic wrap (the wrap should rest directly on top of the pudding). Allow to cool completely.
Whip butter for several minutes until light and creamy. Add cooled pudding by tablespoonfuls to butter and beat until blended. Pour pudding layer onto cooled cake in baking sheet and smooth. Refrigerate cake until ready to pour on chocolate layer.
For the glaze, melt dark chocolate glaze and add coconut oil, stir briefly. Spread chocolate glaze evenly over pudding layer and smooth. Allow to cool. The cake makes about 24 pieces.