For the pastry: 

flour  gr.400
beer yeast   1dice
potatoes gr.100
butter  gr.100
parmisan gr.100
eggs  3 eggs ( 2 reds + 1 white )
salt   1 little spoon 

For the stuffing:

prosciutto gr.120
mozzarella gr 120 
butter to grease gr.50
12 little moulds 

 This is a typical neapolitan dish that you can serve for appetizer or as a main course suite by a salad or a meat.

When the pastry is rising be careful to let it in a very warm place, far from windows or doors or any draught... 

Fist you should prepare a " panetto", little pastry, with the yeast, 50gr of flour and just a little bit of water ( not too cold) and you let it rise 40 minutes; then you boil the potatoes, peel  and  puree them.

Prepare the rest of flour as a circle and in the middle you put potatoes, salt, the "panetto", butter, parmisan and you mix well all adding one by one the eggs. Mix with hands for 20 minutes.Grease with butter the moulds, put 2 fingers of this pastry inside them, and in the center put little pieces of mozzarella and prosciutto; and let rise again in a warm place.When the brioches will be rised enough put them in the oven at about 150° for 20-30 until you see the appear brown.(Marco Bentivoglio)

Wait for a while before serving.