Chelsea bun is a type of currant bun that was first created in the 18th century at the Bun House in Chelsea, an establishment favoured by Hanoverian royalty which was demolished in 1839.
The bun is made of a rich yeast dough flavoured with lemon peel, cinnamon or mixed spice. Prior to being rolled into a square spiral shape the dough is spread with a mixture of currants, brown sugar and butter. The process of making this bun is very similar to that involved in producing the cinnamon roll. After being cooked traditionally the chelsea bun is glazed with cold water and sugar. It is glazed while still hot so the water evaporates and leaves a sticky sugar glaze, making the bun much sweeter.
Recipe for Chelsea bun see Here