• Add the flour, sugar, yeast and salt to the bowl of a stand mixer and whisk to combine.
• Add the cooled tangzhong, softened butter, warm milk, egg and egg yolk.
• Knead for 10–15 minutes, until smooth and elastic!
• Transfer the dough to a lightly oiled bowl using oiled hands.
• Cover with clingfilm and refrigerate overnight to prove.

Vanilla Custard

• Heat the milk in a saucepan until steaming.
• In a bowl, whisk together the egg yolks, sugar and cornflour until smooth.
• Gradually pour the hot milk into the egg mixture, whisking continuously.
• Return the mixture to the saucepan.
• Cook over a medium heat, whisking constantly, until thickened.
• Remove from the heat and stir in the vanilla.
• Transfer to a bowl, cover the surface directly with clingfilm and chill until needed.

Streusel

• Rub the butter into the flour and sugar until the mixture resembles coarse crumbs.
• Refrigerate until needed.

The Next Day

• Remove the dough from the fridge and allow it to sit at room temperature for 30 minutes.

Shape and Prove

• Divide the dough into 11 equal portions, approximately 65–70g each.
• Shape into tight balls.
• Arrange on lined baking trays, leaving space between each bun.
• Cover loosely and leave to prove for 30 minutes, or until slightly puffy.

Fill and Finish

• Using the back of a tablespoon, gently press a well into the centre of each bun, leaving a thick border around the edge.
• Fill each bun with approximately 1½ tablespoons of chilled custard.
• Top with fresh blueberries. About 6 blueberries per bun!
• Egg wash on the exposed dough only.
• Sprinkle generously with the streusel topping and bake!

Bake

• Bake at 170°C fan / 180°C conventional for 18–22 minutes, until golden brown.
• Allow to cool slightly before serving.