Have sheet pans with a light dusting of flour.
In a large bowl mix 1 pound mashed potatoes, 2 egg yolks and 2 tablespoons melted butter or olive oil.
Add 1 ⅓ cups all-purpose flour, 4 tablespoons parmesan cheese, 1 teaspoon salt, black pepper to taste and large pinch of ground nutmeg.
Mix well and dump onto a floured counter. Sprinkle a few tablespoons of flour on the dough, and fold it over itself a few times to integrate.
Gather into a long rectangle, and divide it in 3 or 4 parts.
Take each portion and make long, thin ropes, about the width of a finger. Try to add as little as extra flour as possible, since that will make them tough after cooking. But do add by Tbs if the dough doesn’t come together; you need to be able to cut it into pieces.
Cut small pieces, the size of lima beans. It grows a lot when you boil it. You can slide them down a fork or gnocchi board to create the ribbed surface. Put the individual morsels on the prepared sheets. I like to freeze them for an hour before boiling them as it helps prevent it from becoming gummy or sticking when boiling.
Have abundant salted water boiling in a large pot, they need space to cook.
Meanwhile, put some olive oil in a skillet and add ¼ cup minced spring onions. Cook 1 minute on medium heat and add 2 cups cherry tomatoes, salt and pepper to taste, and let them soften a bit.
Add the gnocchi (in batches if necessary) to the boiling water directly from the freezer. When they rise to the top, they are done. Take them out with a skimmer or slotted spoon and add them to the skillet. You will do this in batches as they won't all pop to the surface at the same time.
Cook over medium/high heat everything together for a minute or two and serve immediately with additional grated parmesan cheese and chopped fresh basil. Alternatively, you can have the sauce ready and plate the gnocchi as you take them out from the boiling water and add the sauce, no need to cook them in the skillet. Whatever feels easier.