Warm milk and dissolve yeast in the milk.
Add sugar, cardamom, oil, and egg, and stir.
Add most of the flour and salt and mix using a machine.
Add more flour if necessary.
Add butter and mix the dough until smooth and elastic for a couple of minutes.
Add the chocolate buttons and knead the dough for 10-20 seconds until the buttons are well distributed in the dough.
Let it rise to double its size - approximately 45 mins.
Shape into buns (12 large, 16 medium, or 20 small) and let them rise again for about 30 mins on a baking sheet, placing them close (2-3 cm apart) so they grow into each other during rising.
Brush with egg and bake for about 13-15 mins at 210 degrees Celsius (410 degrees Fahrenheit) regular oven.
Enjoy them very much.