Preheat the oven to 150C/300F/Gas 5.
For the gnocchi, prick the potatoes several times with a small knife and place onto a bed of rock salt in a baking tray. Bake for about 1½ hours, or until the inside is soft when tested with a knife. When cooked, remove from the oven and set aside to cool.
Remove the cooked potato from the skins and pass through a potato ricer or sieve into a large bowl.
Add the flour, parmesan, egg yolk, olive oil to the potatoes. Season, to taste, with salt and stir until the mixture comes together into a dough.
Working on a floured surface, divide the dough into four and roll each quarter into a long sausage shape. Cut into 2cm/1in pieces.
Once all the gnocchi are cut, drop them into a large pan of boiling salted water. When the gnocchi bob up to the surface, they are ready. Remove with a slotted spoon and place into a bowl of ice cold water to cool. Drain and toss in a little olive oil to prevent from sticking.
For the grilled radicchio and sausage sauce, heat one tablespoon of the olive oil in a frying pan. Add the sausage meat or minced pork belly and fry until golden-brown all over. Add the chopped shallot, garlic, chilli flakes and parsley and cook for two minutes.
Add the chicken stock and simmer until the volume of the liquid has reduced by three-quarters. Add the cream, capers and lemon zest and simmer for two minutes, then stir in a knob of the butter to finish.
Cut the radicchio into thin wedges through the root, so that it holds together. Dress with a tablespoon of olive oil and cook on a grill pan until it starts to colour. Turn the radicchio over and grill for another minute or two then remove from pan.
Fry the breadcrumbs in the remainder of the butter until golden-brown. Season to taste with salt and freshly ground black pepper. Scoop out the crumbs onto some kitchen paper and allow to cool.
Heat the remaining olive oil in a non-stick frying pan and fry the gnocchi until golden-brown all over and piping hot.
To serve, first place the radicchio onto a serving plate, dot the gnocchi over, spoon the sausage sauce over the gnocchi and finish with a little freshly grated parmesan and a good sprinkle of crunchy breadcrumbs.