A Belgian bun is a sweet bun containing sultanas and usually topped with fondant icing and half a glace cherry. The bun is round or square shaped, with rounded off edges, making it similar in appearance to a Chelsea bun.
In a small pan warm the milk until it's lukewarm. Set aside.
Sift the flour into a large bowl and add the yeast. Make a well in the middle and add the butter, sugar, milk and egg. Mix to combine.
Using a dough hook, beat on a medium speed until you have a soft dough - about 10 minutes. (If you are not using a mixer you can knead the dough by hand for this step).
Transfer the dough to a lightly floured surface and knead it by hand for 1 minute. Form the dough into a ball and transfer into a lightly greased bowl and cover loosely with a piece of lightly greased cling film. Leave to rise in a draught-free place until it has doubled in size (around 1 to 2 hours, or overnight in the fridge for a slow-rise).
Generously grease a tray with butter. Set aside.
Once your dough has doubled in size, turn it out onto a lightly floured surface and using a rolling pin, roll it into a rectangle about 10" by 14". It's important to make sure your dough is of even thickness all over to ensure you have nice neat buns.
Spread the lemon curd from edge-to-edge of the dough and sprinkle the sultanas evenly over.
Roll the dough tightly to create a sausage. Cut the sausage into 6 buns - I tend to cut in half, then thirds to ensure even buns. Arrange the rolls in your pre-greased tray and cover loosely with a piece of lightly greased cling film.
Leave to rise in a draught-free place for 1-2 hours until they look light and puffy.
After your buns have gone through their second rise, remove the cling film and place the tray in a pre-heated oven at 180°c (160°c for fan assisted ovens) and bake for around 10-15 minutes until golden brown.
Transfer to a wire rack when cool enough to touch and leave to cool completely.
For the Icing
In a medium bowl, mix the icing sugar with the warm water, adding a tablespoon of water at a time. When of a "gloopy" consistency, dip the top of each bun into the icing to get an even topping, spreading off the excess with a clean finger.
Finish with half a glace cherry on top of each bun