Drain the mirabelle plums well, collecting the juice. Cut into small pieces. Preheat the oven to 200 ° C. Put all the ingredients for the crumble in a bowl and knead until crumbly.
For the dough, mix flour and baking powder, sieve into a sealable bowl, mix with sugar, vanilla sugar and salt. Add eggs, butter and mirabelle juice. Close the bowl tightly and shake vigorously. Mix everything well again.
Spread the dough on a greased baking sheet. Spread the mirabelle pieces on top. Sprinkle the coconut crumble on top. Bake the cake for about 30 minutes and let it cool down well.