To make pesto, add 2 cups lightly packed spinach, basil, olive oil, lemon juice, Parmesan and pine nuts to a blender or food processor. Blend into a smooth and even paste. Set aside.

Preheat oven to 425°, and prick potatoes with a fork. Place on a baking sheet or pie plate, and bake potatoes for 45–60 minutes or until very tender when poked with a fork. (Check smaller ones, and remove from oven earlier.) Use an oven mitt to hold each potato, and peel.

Press hot potatoes through a ricer, food mill or medium-mesh sieve into a large bowl. Set aside.

In a small bowl, whisk together egg yolks, salt and pepper. Make a well in the center of the potatoes, and add the egg mixture to the well. Stir to combine. Add ¾ cup of flour and 2 tablespoons of the pesto, stirring just until combined. Turn out onto a lightly floured surface. Knead in just enough of the remaining flour, if needed, to make a smooth, fairly soft dough. To keep the gnocchi light, do not overknead or add too much flour.

Divide dough into four portions. Roll each portion into a long, thin log, about 1-inch thick, and cut into ½-inch pieces. Roll each piece into a little ball. Roll balls over lightly floured tines of a fork (this will help them hold the sauce). Place onto a clean towel or baking pan lightly dusted with flour. Set aside until ready to cook.

In a large pot, bring a large amount of lightly salted water to boiling; then reduce heat to a slow simmer. Add half of the gnocchi, stirring so they don’t stick together. Cook about 2 minutes or until they rise to the top. Remove with a slotted spoon to a colander, and repeat with remaining gnocchi. Place gnocchi in a bowl and toss with as much of the pesto as is needed to coat thoroughly (about 4–5 generous tablespoons).

Return cooking water to a boil and toss remaining 2 lightly packed cups of spinach into the hot water. Remove immediately with a slotted spoon as they wilt (just a few seconds), and strain. Mix spinach into the gnocchi and pesto. Serve with additional Parmesan.