How to make rhubarb yeast buns with crumble topping

• Add yeast and sugar to lukewarm milk and mix thoroughly. Cover and set aside in a warm place for about 15-20 minutes for the yeast to activate - during this time it should rise and become very foamy.
  100 ml milk, 15 g yeast, 1 teaspoon sugar
  
• Place the ingredients for the yeast dough in a mixer bowl. Add the yeast starter and begin to knead the dough.
  250 g wheat flour - all-purpose, 30 g sugar, 50 ml oil, 1 egg
  
• The dough is well-kneaded when it is nicely smooth. Then cover the bowl with the dough with a cloth and set aside in a warm place for about an hour - the dough should double in volume.
  
• Wash the rhubarb, cut off the ends, and slice the rest into pieces about 1 cm thick. Add sugar to it and mix.
  approx 250 g rhubarb, 2 tablespoons sugar
  
• Briefly knead the risen dough again, then divide it into eight roughly equal parts - I weighed the buns - each was about 60 g.
  
• Arrange the buns with space between them on a large baking sheet lined with parchment paper.
• Using a glass lightly floured on the bottom, make an indentation in each bun.
  
• Press the glass down firmly so that the dough spreads out to the sides.
  
• Place the rhubarb into the indentations.
  
• Briefly combine the crumble ingredients - you can knead them with your fingers, mix with a fork, or like me, briefly blend in a food processor.
  50 g butter, 70 g wheat flour - all-purpose, 45 g sugar
  
• Sprinkle the crumble topping over the buns.
  
• Cover the buns with a cloth and leave for about 30 minutes to puff up.
• Meanwhile, preheat the oven to 170 degrees (fan-assisted).
• Bake the buns for about 20 minutes - until golden brown. After baking, let them cool slightly and you can eat them while still slightly warm :)