Make the filling by mixing together the melted butter, cocoa powder, espresso powder (or coffee granules), brown sugar and chocolate. Set aside.
Grease a loose-bottomed round 20cm/8in cake tin. Preheat the oven to 180C/160F Fan/Gas 3.
For the dough, put the self-raising flour, salt and sugar into a bowl and give it a quick mix.
Put the melted butter, vanilla paste, egg yolks and milk into a smaller bowl, and whisk until combined.
Make a well in the centre of the dry ingredients and pour in the wet ingredients. Use a palette knife to mix it all in, then get your hands in and bring everything together until you have a smooth dough.
Throw a little flour on a work surface and drop the dough on top. Roll it out to a rectangle about 30 x 25cm/12 x 10in.
Spread the filling all over the dough, evenly, making sure to get all the way to the edges. Roll it up, starting from the long edge of the rectangle.
Cut the roll into 9 equal pieces and drop them on to their sides so you can see those beautiful swirls. Using the chubby part of your hands, just give them a little push – this will encourage the rolls to stick together and get rid of gaps. Place them on their sides in the prepared tin, making sure to have those swirls on show.
Brush the swirls with milk and pop into the oven for 30–35 minutes. You will know they are ready when they are golden on top and the rolls start coming away from one another.
Leave to cool completely in the tin. This will help the icing to set better on top and not simply run off. You can eat these warm, but be warned, you will chase the icing.
Make the icing by mixing together the boiling water and espresso powder. Give the mixture a few minutes to cool, then add the butter, cream cheese and icing sugar and mix until you have a thick coffee-flavoured icing. Drizzle the icing all over the top of the cooled swirls.
Take out them of the tin and the swirls are ready to serve.