Method

• 1.
  Place yeast and 1 tsp caster sugar in a bowl with 200ml warm water and stir to combine. Set aside for 5 minutes or until foamy.

• 2.
  Meanwhile, place flour and remaining 50g caster sugar in a stand mixer fitted with the dough hook. Make a well in centre of flour mixture. Whisk egg yolks into yeast mixture, pour into well and stir to combine. Knead on medium speed for 2-3 minutes or until a stiff dough forms. With the motor running, add 250g softened butter, 1 piece at a time, until butter has been incorporated into dough. Knead for 8-10 minutes or until the dough is smooth.
• 3.
  Transfer dough to a greased bowl, cover with plastic wrap and set aside for 2 hours or until doubled in size. Knock back dough.
• 4.
  Line a 22cm x 40cm tray with baking paper and spread dough evenly over tray. Melt remaining 100g butter and cool. Brush melted butter over dough, then scatter cinnamon and brown sugar evenly on top. Cover with plastic wrap and chill overnight.
• 5.
  The next day, cut the sheet of brioche in half lengthways. Stack pieces on top of each other, sugar crust on the inside and cut into nine 4cm fingers. Place fingers in a 36cm x 14cm loaf pan, cut-side up, scatter with a pinch of salt flakes and cover with a clean tea towel. Set aside in a warm place to prove for 1 hour.
• 6.
  Preheat oven to 170°C. Brush brioche with egg. Bake for 25-30 minutes or until golden.
• 7.
  For icing, place all ingredients and 2 tbs warm water in a food processor and whiz until smooth and combined. Drizzle over loaf to serve.