In the meantime, prepare the filling: put the ricotta in a container, add the boiled and cut chard, along with the grated Parmigiano Reggiano, egg and salt and mix everything together with the grated nutmeg.
Roll out the pasta with a rolling pin to obtain a thin sheet. Place the pasta on a work surface and place a teaspoon of filling (for each tortello) on top and then cover it with the pasta, try not to leave any air holes that could cause the tortello to break up during cooking.
Prepare a dish that has some knobs of butter on the bottom, place the well-draned tortelli on top and cover with a layer of Parmigiano Reggiano on top.
Wash and cut the fennel into julienne strips, put it in a bowl with the juice of half a squeezed orange, salt and pepper and a spoonful of extra virgin olive oil.
Cover with clingfilm and leave in the fridge to allow the flavour to develop.
Put a whole egg, the salt, juice and zest of half an orange in a narrow, tall-sided bowl. Start blending with a hand-held mixer gradually adding the seed oil until
you obtain a dense, foamy cream. Cover with clingfilm and place in the fridge for a few minutes.
When the orange mayonnaise has become firm, cut the bread rolls in half and spread with the mayonnaise.
Top with slices of mortadella and thin strips of marinated fennel.