Add flour to a stand mixer bowl. With a cooking spoon, shape a well in the middle and add 1 tbsp. sugar, yeast, and about half of the lukewarm milk to the well.

Mix the ingredients in the well while incorporating a small amount of flour from the rim of the well.

Cover the bowl with a clean kitchen towel and allow to sit for about 15 min. in a warm place.

Add the remaining ingredients to the bowl and knead for about 10 min. or until the dough is smooth and shiny.

Cover the bowl with a kitchen towel once more and set aside in a warm place for about 2 hours, or until the volume has doubled.

In the meantime, wash the plums, remove the stem, and cut the plums into halves, and then cut each half into 3 or 4 pieces. Peel the apples, remove the core, and slice into small slices.

Cut the butter for the streusel into small cubes and add them with the flour, sugar, cinnamon, and vanilla sugar to a medium-sized bowl. Knead the ingredients until crumbles form.

Preheat the oven to 350 °F.

Grease a baking sheet and flour lightly. Roll out the yeast dough and arrange the plums and apple slices on top of the dough.

Sprinkle with cinnamon to taste and spread streusel evenly over the fruit.

Bake for about 25 - 30 Min.