Rhubarb and strawberry sweet buns — fluffy yeasted pastry recipe

These rhubarb and strawberry sweet buns use a classic yeasted dough made with a starter (rozczyn) of yeast, sugar, flour and warm milk left to rise for 20 minutes. The dough is kneaded for 15–20 minutes, then softened butter is added in stages before a final rise. The buns are filled with seasonal fruit and baked in a home oven.