- Combine bread flour, yeast, salt, and black sesame seeds in a bowl, then add warm water and olive oil and knead for 10 minutes until smooth and elastic. Cover and prove for 1 hour until doubled in size.
- Slowly cook sliced onions in butter over low heat for 30–40 minutes, stirring occasionally, adding a teaspoon of brown sugar halfway through until deeply caramelised and jammy.
- Slow-cook chicken with garlic and chicken stock in a covered pan over low heat for 25 minutes, then shred finely using two forks and season well with salt and black pepper.
- Blanch asparagus spears in boiling salted water for 2 minutes, then transfer immediately to ice water to keep vibrant green, and cut into 4cm pieces.
- Mix the pulled chicken with caramelised onions, asparagus pieces, and grated cheddar to form the filling.
- Divide proved dough into 2 equal portions, flatten each into a disc roughly 18cm wide, place a generous mound of filling in the centre, then gather the dough edges up and around the filling, pinching firmly to seal into a tight ball.
- Place sealed-side down on parchment-lined tray, sprinkle tops with extra black sesame seeds, and prove for a further 20 minutes. Bake at 200°C for 22–25 minutes until golden.
- Rest for 5 minutes before serving — the buns will be very hot inside.
Tip: The key to a leak-free bomb bun is ensuring your filling is not too wet — pat the asparagus dry after blanching and drain any excess liquid from the chicken mixture before assembling, otherwise steam will cause the dough to split during baking.