Cardamom, grapefruit, hazelnut and white chocolate tear-and-share buns

Method

1. Mix both flours with the yeast, salt and 50g of the sugar in a bowl, then make a well in the centre. Put the milk and cardamom in a small pan and heat until lukewarm. Pour into the well, followed by the eggs, then mix into a smooth dough. Tip onto a lightly floured worksurface or into a stand mixer with a dough hook. Knead by hand for 12 minutes (or 8 minutes in a stand mixer on a low-medium speed) until springy to touch.
2. Continue to knead the dough, adding 160g of the butter a few cubes at a time, ensuring it’s fully incorporated before adding more (see Be A Better Cook); the dough will be quite sticky at first but will get easier to work, so don’t add more flour. This will take 30 minutes by hand or 20 minutes in a stand mixer on medium speed.
3. Put the dough in a clean bowl and cover with a clean damp tea towel or a clean shower cap. Put somewhere warm for 1-2 hours until doubled in size.
4. Meanwhile, mix the remaining 60g butter with the grapefruit zest, hazelnuts, chocolate and remaining 60g sugar in a bowl.
5. Once the dough has risen, turn it out onto a lightly floured worksurface and divide into 24 balls (about 30g each). Holding a ball in your palm, use your fingers from the other hand to press a dimple into the middle. Spoon 1 tsp of the hazelnut filling into the dimple, then enclose the dough around it. Pinch to seal, then roll on the worksurface to make a neat ball. Repeat with the remaining balls.
6. Sit the balls inside the cake tin, starting from the outside to make a spiral shape into the centre. There should be a bit of space between them. Re-cover with the tea towel and put in the fridge to prove overnight.
7. In the morning, remove the buns from the fridge and leave somewhere warm to prove for 1-1½ hours until puffed up. Heat the oven to 180°C/160°C fan/ gas 4. Brush the tops of the buns with a little milk. Bake for 40-45 minutes until golden brown.
8. Meanwhile make the glaze. Put all the ingredients in a small pan and cook over a medium heat, whisking constantly until combined into a smooth glaze.
9. Allow the buns to cool in the tin for 10 minutes, then transfer to a cooling rack set over a tray. Pour over the glaze and leave to cool for at least 20 minutes before digging in – they’re lovely warm, but if too hot they’ll seem gummy. Any leftovers will keep in an airtight tin for up to 3 days