1. Heat oil in a large heavy-based frying pan. Fry the shallots, celery and the garlic on medium heat for 1-2 minutes or until the shallots turn translucent and slightly golden and the garlic smells fragrant. Add the tomatoes, season with salt and cook on medium-low heat for 15-20 minutes. Turn off the heat and add basil leaves. Cover with a lid and set aside.
2. In the meantime, make the gnocchi. Discard any excess liquid from the ricotta and put it in a large mixing bowl with the egg yolks, parmesan cheese, salt and pepper. Add the flour and work with floured hands or a wooden spoon until you have smooth soft dough – it should be pliable and a little sticky but not too wet.
3. Flour your hands and cooking bench generously and divide the dough into 6 pieces. Take 1 piece, sprinkle it with flour and roll it with your hands to form a log. Cut the log into small pieces and set aside on a floured wooden board. Repeat with the remaining dough.
4. preheat your oven to 200 C.
5. Bring a large pot of salted water to the boil and drop the gnocchi in, in two or three batches, stirring gently. Cook for 1–2 minutes or until they come up to the surface, lift them out with a slotted spoon and drop them straight into the pan with the tomato sauce. Repeat until all the gnocchi is cooked. Coat them well in the sauce.
6. Place the gnocchi and sauce in a large oven safe dish. Distribute the Bocconcini evenly, grate parmesan on top and bake for 15-20 minutes or until the cheese has melted and the gnocchi looks golden.