In a generous quantity of salted water, boil the spinach and the chard for around 5 minutes.
Drain and finely chop the vegetables.
In a pan, heat the extra-virgin olive oil and sauté the lard, the ½ onion and then add the spinach and chard.
Cook everything for approx. 5 minutes.
Add the grated bread crumbs and continue cooking for another 3 minutes.
When the mixture has cooled, add the Parmigiano Reggiano and egg, then mix well.
Roll out the pasta dough, and cut it into strips.
Add the filling to the centre, creating tortelli or ravioli.
Cook in salted water, then gently drain and arrange the tortelli in a serving dish, adding butter and Parmigiano Reggiano to taste.
Before serving, add a few drops of Traditional Balsamic Vinegar from Reggio Emilia, in its first stages of aging (from 12 to 20 years).