Heat a large pot with the olive oil and sweat off the onions and garlic until softened.
Add the bay leaves and basil, and mix in the tomato passata. Season with salt and pepper and cook on a low to moderate heat for about 35 minutes until the consistency of sauce. Adjust seasoning if needed.
Place the unpeeled potatoes in a large pot and cover with water. Bring to boil and turn down heat so water is simmering. Cook potatoes until you are able to easily skewer them.
Once cooked, remove potatoes from water and briefly roast in hot oven until dry. Peel off skins.
Pass potatoes through a ricer on to a work surface. Make a well in the centre of the potato mixture.
Place egg yolks, grated nutmeg, salt and the flour into the well and gently mix the potatoes into the centre. Knead the potato mix until a firm dough has formed.
Bring a large pot of salted water to boil. Flour the bench top and cut a piece of the dough and roll out into a thick roll, approximately one inch in diameter.
Cut the roll into ¾-inch-long pieces and roll each piece onto a gnocchi board.
Cook gnocchi in boiling water. Remove with a sieve or slotted spoon once gnocchi has risen to the surface of the water.
Gently place gnocchi into the passata and toss through the sauce. Serve with a generous amount of grated pecorino romano.
