A Belgian bun is like a Chelsea bun, but with icing and a cherry on the top and filled with homemade lemon curd and juicy sultanas. The trick to a perfect Belgian bun lies in the roll – you want it tight, but not too tight. The roll needs to give the dough room to expand during proving, so that the buns rise outwards rather than being forced upwards, and so that the end of the roll stays stuck in place.
Make the dough. Place the flour, sugar and salt into a large mixing bowl and stir until thoroughly combined. Make a well in the centre and tip in the yeast.
Warm the butter and milk with 120ml of water in a small saucepan until the butter is melted and the mixture is lukewarm. Pour this into the flour mixture, and stir thoroughly until the contents of the bowl come together as a soft dough.
Tip out the dough onto a lightly floured work surface and knead well for 5 minutes, until the dough is smooth and elastic. Place the dough into an oiled bowl, cover and leave it to rise, for 1 hour, or until doubled in size.
Make the curd. Put the lemon juice and zest, sugar and butter into a heatproof bowl. Sit the bowl over a pan of gently simmering water, making sure the water is not touching the bottom of the bowl. Stir the mixture every now and again until all the butter has melted.
Lightly whisk the egg and egg yolk together in a bowl and then stir them into the lemon mixture. Whisk until all the ingredients are well combined, then leave the mixture to cook for 8–10 minutes, stirring every now and again, until the mixture is creamy and thick enough to coat the back of a spoon. Remove the lemon curd from the heat and leave it to cool, then chill it until set.
Tip out the dough onto a lightly floured work surface and roll it out into a rectangle measuring about 30 x 40cm with a short end closest you. Tack down this end by pressing it down onto the work surface with your thumb.
Spread the lemon curd over the dough and sprinkle it with the sultanas. Starting at the short end furthest away from you, roll the rough towards you quite tightly until the roll is complete. Using a sharp knife, cut the dough roll into 12 thick rounds.
Arrange the bun on the prepared baking sheets, spacing them well apart. Place each baking sheet into a proving bag and leave the buns to rise for 45 minutes, until doubled in size.
Heat the oven to 200°C/180°C fan/400°F/Gas 6. Brush the buns with a little egg wash. Bake the buns for 10 minutes, then reduce the oven to 180°C/160°C fan/350°F/Gas 4 and cook them for a further 10 minutes, until golden brown. Remove the buns from the oven, leave them to cool slightly then transfer them to a wire rack to cool completely.
Make the decoration. Mix together the icing sugar, lemon zest and about 2 tablespoons of water to make a stiff, but pourable icing. Dip the buns in the icing, then allow any excess to drip off. Top with half a glacé cherry and leave to set before serving.