Ingredients
300g milk
7g Packet of active dry yeast
500g strong white bread flour, plus extra for dusting
80g caster sugar
½ tsp fine salt
1 egg
100g butter, cubed and room temperature

Ingredients for the filling
180g soft butter
300g soft light brown sugar
3 tablespoons ground cinnamon

Ingredients for the glaze (optional)
100g caster sugar
1 tbsp lemon juice
1 cinnamon stick

Ingredients for the sugar topping (optional)
2 tbsps caster sugar
2 tbsps light soft brown sugar
1 tbsp cinnamon

Method
Warm the milk to 37c (or just warm) and put the yeast into it, stir and put to one side for 5 minutes.

Meanwhile, put the flour sugar and salt into your stand mixer with a dough hook attached and mix through for 30 seconds or so.

Add the whole egg to the milk and briefly mix through.  With your stand mixer going, slowly add your milk mixture and leave running for roughly 5 minutes until a sticky dough forms.  Add ¼ of the soft butter and turn the mixer back on and kneading for a couple of minutes until fully incorporated.

Repeat this with the next ¼ and repeat two more times.  Your final kneading time will be around 5 minutes.  You will know the dough is ready when it is smooth and glossy.  Very lightly grease a clean bowl with a little butter, put the dough in, cover with cling film and put into the fridge for an hour.

Once the dough has rested for an hour, make the filling. Put all of the ingredients together in your stand mixer and beat until incorporated.

Put your dough onto a lightly floured work surface and roll out to a rectangle, about 50 x 40 cm. Turn the dough so the long edge is at the bottom and top.  Spread the filling mixture evenly over the dough, leaving a small 1cm strip at the bottom without filling.  Brush the bottom edge with water and roll the dough up, starting from the top long edge.  Press the wet edge to seal.  Turn the dough over so the seam is at the bottom.

Cut the log in half and then each half into 6 equal pieces, so you have 12 pieces in total, each piece should be about 5cm.

Now you can either bake into a 12 hole muffin pan or, get a 23cm cake tin.  Whichever you are using, grease the tin with a little butter.  Carefully put them into the holes of the muffin pan and gently press them put down or, put them into your tin, maneuvering them until they all fit, again gently pushing down. 

Preheat the oven to 200c. Cover with cling film and leave to prove in a warm place for about 1 hour until roughly doubled in size.

Before putting into the oven, mix the egg yolk with 1 tsp of water and put over the top of your buns.

Put the buns into the oven and immediately reduce the heat to 180c and bake for 15 minutes.  After 15 minutes, turn the so the front is now at the back and bake for a further 10-15 minutes until puffed up and golden brown. Leave to one side for a few moments until cool enough to handle.  If you are using a muffin tin then I just run a butter knife around the edge as soon as they come out of the oven.  After a few minutes remove the buns from the tins and put onto a cooling rack.

Meanwhile, make the glaze or the sugar topping if using.  Put all the glaze ingredients into a small saucepan and over a medium heat, cook until the sugar has dissolved.  Once dissolved, increase the heat and bring to the boil.  Without letting it boil over, cook for couple of minutes to thicken slightly. Remove from the heat and, using a pastry brush, liberally spread over your buns. 

For the topping, mix the sugar and cinnamon in a large shallow bowl then, once the buns are cool enough to handle, roll them gently in the topping to coat.