Blueberry brioche buns

Dough

• 100 g unsalted butter cut into pieces
• 100 g white sugar
• 2 tsp dried instant yeast
• 250 g full cream milk
• 500 g plain flour
• 1 egg
• 5 egg yolks (see Tips)
• 1 pinch sea salt
• oil to grease
• plain flour to dust

Filling

• 250 g fresh blueberries or frozen blueberries, thawed and dried with paper towel
• 1 - 2 tbsp icing sugar
• 2 tsp cornflour
• 150 g icing sugar
• 35 g freshly squeezed orange juice