Yeast cake with blueberries and crumble: step-by-step recipe

This yeast cake with blueberries and crumble starts with a pre-ferment: fresh yeast rubbed with a spoonful of sugar, warm milk and flour, left to rise for 15 minutes. The dough is then made by combining the pre-ferment with flour, eggs, sugar, salt and gradually added soft butter, kneaded for about 15 minutes until smooth. The provided text cuts off before the blueberry filling and crumble steps.