In a large bowl, mix together the warm water, milk, yeast and 1 teaspoon of your caster sugar. Leave to stand for about 5 or 10 minutes. It should start to bubble a little bit. 

Next add the melted butter, egg and the rest of the sugar to the yeast mixture and give it a whisk.

Add the flour and salt to the yeast mixture a little bit at a time and continue to whisk.

Once it starts to form a dough it's easier just to mix with a wooden spoon. Turn the dough out onto a lightly floured surface and knead for 10 minutes. 

Pop the dough back into the bowl, cover the bowl with cling film and leave to prove for 1 hour at room temperature. It should roughly double in size.

On a floured surface, roll the dough out into a rectangle about 45cm by 25cm. The dough should be about the thickness of a £1 coin.

To make the filling, stir together the brown sugar, cinnamon and vanilla extract.

Brush (or just use the back of a spoon) the softened butter onto the dough rectangle and then tip over the yummy cinnamon sugar mixture onto the dough and evenly spread it out across the rectangle.

Roll the dough into a cylinder (a bit like a Swiss roll), with the longer edge facing you and rolling from left to right. SO hard to explain what I mean here but basically end up with a cylinder that is 45cm in length rather than 25cm which it would be if you rolled it the wrong way.

Score the top of the cylinder so that you end up with enough to make 12 rolls. I stupidly didn't take a picture of this bit but hopefully that makes sense. Each score should be about 2 inches apart. 

Top tip. Instead of cutting the dough with a knife, use a piece of string to tie round the cylinder and then match it up with the knife score and pull and it should create a clean cut. Here's a YouTube video on what I mean.

Put the rolls into a lightly greased, deep baking tray. Cover with clingfilm and leave to prove for 45 minutes.

Melt a couple of tablespoons of butter and brush it over the rolls to give them a nice shine. 

Bake for 20-25 mins at 190C (170C fan, gas mark 5) until golden brown. Leave them to cool. They smell incredible.

While they cool, make the buttercream topping. Melt the butter and add the icing sugar, vanilla and milk. Give it a whisk and pour over the rolls.

Enjoy with a nice cup of coffee or, if you're my brother, some Irn Bru.