Add milk, dry yeast, and sugar in the bowl of a stand mixer and mix everything with a whisk.
When the yeast is dissolved, add the beaten eggs and mix again with the whisk.
Add the flour and turn on the stand mixer (with the hook) to start kneading all the ingredients (or you can also knead by hand!)
When a dough is formed pour the salt and keep kneading. You can now start to add the soften butter a bit at a time. Wait until the butter is completely absorbed into the dough before adding another piece.
Lastly, add the chocolate chips a bit at the time. Continue to knead until the chocolate chips are completely incorporated and dough is smooth and elastic.
Remove the dough from the bowl and transfer it on a table. Shape the dough into a ball, put it back into the bowl and let it proving until it has doubled in size (approximately 2-3 hours depending on the external temperature)
Once the dough has proven, put the bowl into the fridge for at least 20 minutes. This will ensure that the chocolate chips do not melt when you will start working the dough with your hands to form the pangoccioli.
Remove the dough from the fridge, transfer it on the table and cut it into 12 pieces of approximately the same size. Roll all the pieces into balls (start by pulling the edges towards the center, turn the seam side down and circle using hands) and arrange your pangoccioli on a lined baking tray. Let them proving again for approximately 45 minutes/1 hour.
Your pangoccioli can now go to the oven. Brush their surface with some egg wash and a cook in the oven at 180° for 10-15 minutes (the surface must be golden brown).
Your pangoccioli are ready! You can keep them in a airtight container for 2-3 days and briefly warm them up in the microwave or in the oven before eating them. Alternatively, you can freeze them so that they can last for several months.