Since some months I did not bake breads made with sweet starter alone. But just now my starter is so active as never before. It just need 90 minutes to double its volume. It is in the perfect condition to rise even a bit heavier dough with some butter. And so it is in the perfect condition to rise burger buns.
You need a real fit starter, so it makes sense to feed it two or three times before baking. Another important point is proofing the buns in a warm environment. The warm environment can be a slightly heated oven (30°C), then add a pot with boiling water on the bottom of the oven. This helps to keep the surface of the buns warm and moist and let them rise very well.
The aroma of the buns is delicious, the cold rise of the dough and the combination of hazelnut oil and butter makes them very flavourful. The hint of hazelnut flavour goes very well together with my favourite vegan patty. But my dearest liked it very much in combination with a beef patty, too.