BRIOCHE DOUGH

1. Combine the ingredients. Place all ingredients except for the butter into a medium bowl. Bring together into a rough dough, then turn out onto a work surface (do not add more flour). Knead the dough for 8-10 minutes. It will start off as very rough, then will come together and become smooth and elastic, and when pressed lightly with a finger, the dough should spring back slightly.
2. Add the butter to the dough. Flatten the dough out into a rough rectangle and add the butter to the surface of the dough. This part will get sloppy, so make sure that you have a bench scraper nearby. Incorporate the butter into the dough by squeezing it and kneading it in. Keep scraping any excess butter back onto the dough and kneading it in. Don’t freak out. It will all work together. Once the butter has incorporated into the dough, knead for a further 2-3 minutes.
3. Leave dough to rise. Shape the dough into a ball and then transfer to a lightly buttered bowl. Cover with plastic wrap. Leave to sit on the counter for about 20 minutes to kick start the rising process, then transfer to the fridge to rise for at least two hours, and up to overnight. 

ASSEMBLY

1. Make the filling. Combine all filling ingredients in a bowl and mix until well incorporated. Grease a muffin pan with melted butter and a brush - you need 8 holes of the pan filled. If you are worried about the buns sticking, you can place a small piece of parchment paper into the cup of each pan to help with removal. I like to leave a gap between rolls where I can - with 8 holes in a 12 cup muffin pan there will be some with rolls next to each other.
2. Roll out the dough. Turn the chilled dough out onto a lightly floured surface. Shape into a rectangle by patting down and squaring off the edges with a bench scraper. Starting with the dough in a rectangle means you are more likely to get a nice even rectangle of dough when you roll it out. Roll the dough to a rectangle that is 32x36cm (12.5 x 14 inches).
3. Add the filling. Spread the dough evenly with the filling using an offset spatula. Take it right to the edges. 
4. Fold up the dough. Holding one of the SHORT ends of the dough, fold the dough into thirds like you would a business letter. To do this, take one end and fold it to 2/3 of the way across, then fold the other third over it. (see video at top of post for demonstration). You should now have a rectangle of dough that is 12cm (4.7 inches) wide and 32 cm long. Pat the rectangle of dough out gently just to make sure there are no air bubbles. 
5. Cut into strips. Arrange the dough so one of the short sides is facing you. Cut the dough into 8 strips, each 4cm (1.5") wide (so you will be left with 8 strips each measuring 4x12cm / 1.5x4.7". Place the strip of dough onto a parchment paper lined sheet pan, cover lightly with plastic wrap, and chill in the fridge for 15 minutes. This helps firm up the dough and set the filling, and makes the next step a little cleaner.
6. Shape the cinnamon buns. Remove the dough from the fridge. Working with one piece of dough at a time, cut the strip of dough into 3 pieces, leaving an end intact (see images). Braid the strips of dough together to form a single braid. Starting with the clean joined end, roll the whole braid up into a ball. Place into one of the cavities of the muffin pan. Repeat the process with the remaining strips of dough until you have 8 buns. Cover the pan lightly with plastic wrap, and leave in a warm spot until the buns are puffy and when pressed lightly with a finger, the dough an indentation is left that slowly springs back, about 45 minutes to an hour.

BAKING

1. Prepare the buns for baking. Toward the end of the rising period for the buns, preheat the oven to 375°f / 190°c. Remove the plastic wrap from the risen buns, and brush the tops with egg wash, being careful not to drip too much down the sides or brush too much of the filling onto the dough. 
2. Bake the buns. Bake the buns for 15-20 minutes, until they are golden brown. If you like, you can measure the temperature of the buns with a probe thermometer inserted into the dough. Fully baked dough reads at about 190°f / 90°c. Remove the buns from the oven and transfer them to a wire rack soon after removing them, so that they do not stick to the pan. Leave to cool on the wire rack. Dust with powdered sugar and serve. 

Store leftovers in an airtight container at room temperature. You can rewarm briefly in the microwave if you like.