After 45 minutes, switch the oven to 190C to preheat. At this point, check the status of the buns. It’s really important to proof the dough to 100%, i.e. to the maximum possible. This yields the softest buns. To check that the dough is ready for baking, wet your finger and use lightly poke the dough. The indent should be visible, and only fill back very slowly, and not to the full extent. Start checking in 45 minutes and then every 10 minutes after that.