Mix the dry yeast with flour, knead the egg, sugar, salt, rum, milk and the lukewarm butter well, press this soft dough into a prepared springform pan (with wet fingers).
For the crumble mix all the ingredients (coarse fork) and distribute on the cake base (becomes a thick layer) - bake at 160 ° convection for approx. 30 min (not preheated) - sprinkle with icing sugar when cold.