For preparing the piadina
If you use lard, heat the water in a saucepan, melt the lard and set aside.
If you have a kneading machine, pour the flour, yeast, bicarbonate and salt in the bowl, knead for a few seconds and add the lard dissolved in the water, or the extra virgin olive oil and some water. Start with 350g of water but add more until the dough is soft but not sticky. The amount depends both on the flour used and on the weather. Consider that you may need 400/430g. Start the mixer at medium speed and mix the ingredients until you have a smooth and compact dough. If you are kneading by hand, put the ingredients in a bowl, following the same procedure as above
With the help of a spoon, mix the ingredients until compact, then transfer to a pastry board and knead by hand until you have a smooth, homogeneous ball. Form a dough, cover with cling film or place in a plastic freezer bag and leave to rest for about 40 minutes.
For the garnish
Wash the savoy cabbage, remove the leaves one by one and cut them into small pieces. Pour water into a pot, bring it to boil, add salt and pour in the cabbage. Lower the heat and boil for about 20 minutes. It should be soft. Drain the kale very well, using a sieve and your hands to squeeze out all the water. Pour some oil in a frying pan (savoy cabbage needs plenty of oil), a clove of garlic, the squeezed cabbage and the sausage paste, which you will simply chop with your hands. Cook for about 15 minutes. Remove from the heat and leave to rest before stuffing the piadina.
Take about 160g of piadina dough, roll it out into a circular shape, stuff one half of the disc with the savoy cabbage and sausage. Fold it back on itself, like forming a half moon. Prick the surface with a fork and cook on a hot plate on both sides.