In a small bowl, whisk together the yeast, sugar, warm water and milk. Set aside.
Sift the flour into the bowl of your mixer and add the butter. Using the mixer’s paddle attachment, mix the butter and flour together until it becomes a sandy texture.
Change the attachment to the dough hook and add the egg, salt and yeast mixture. Kneed on the lowest speed for 10 minutes, or 20 minutes if you’re doing by hand. The dough should become elastic, smooth and sticky. Use a spatula or wooden spoon to transfer the dough into a large greased bowl. Cover with plastic film and place in a warm area to rise for 2 hours or until it’s doubled in size.
Transfer the dough onto a floured surface and knead the dough for a minute more. Roll it into a big sausage and cut it into 8 equal size pieces. Flour your hands and take the time to roll each piece into a perfectly smooth ball.
Cover two baking trays in baking paper and place 4 buns on each tray. Make sure you give them enough space as they’ll rise again. Cover with a clean tea towel and allow to rise for another hour.
Preheat the oven to 200°C.
Whisk together the milk and egg and gently brush a thin coat over each bun. Bake for 15 minutes or until golden brown.