The airy flesh of the ubiquitous russet potato makes it the perfect choice for gnocchi. To create light, pillowy gnocchi, make sure that your dough is neither too wet nor overworked. Armida uses the fine markings of the back of her cheese grater to mark the gnocchi; I recommend using the fine side of a box grater to do this, or forming the gnocchi and running them along a wire whisk to mark them. The gnocchi are wonderful with Armida’s easy, rich ragu. They are also delicious with a simpler dressing of melted butter and grated cheese.