Make the butter turn to room temperature.
Heat up the milk so it is luke warm (just below 37°C (99°F) then mix in the yeast. Whisk in the egg.
Mix all the dry ingredients in your food processor and then add the milk mixture and the butter.
Knead for a couple of minutes (5 minutes should do the trick)
Cover dough with a towel and let it rest for 1 hour
Split the dough into 6 equal parts and form them into round balls
Place them on a parchment paper on a baking sheet (leave some space in between since they will expand)
Cover with towel and let it rest for at least another 30 min
Heat up the oven to 225°C (437°F)
Brush the buns with the egg and place the baking sheet on the bottom part of the oven for around 7-8 min
Let it cool under a towel
Take a sharp knife and cut off the top lid, scoop out around half of the inside of the bun.