Preheat oven to 400'F.
Wash and scrub the potatoes clean under cool running water and pat dry. Remove any eyes/blemishes.
Wash potatoes and poke several holes in them before placing them on a baking sheet on the middle rack in the oven, 45-60 minutes, until tender/done. (Test by poking a fork into the potato
Poke a few holes in each potato using a fork.
Place potatoes on a non-stick baking sheet and bake for 50 to 60 minutes. Rotate after 25 minutes. After 45-50 minutes, check potatoes for doneness by poking with a fork. Potatoes are done baking when the skin looks crisp/dry and you can easily poke into the potato with a fork.
When done, remove from oven and let cool. When cool, remove skin from potatotes.
Using either a ricer or a cheese grater or a fork, press/grate potatoes into a bowl until they resemble rice. See photo.
Once potatoes are riced, place into a large bowl and make a well in the center. Add 2 egg yolks, 1/2 tsp salt, and 1 cup flour. Knead dough until ingredients are combined.
Once kneaded into a dough, take a handful of dough at a time and roll into a log approximately 1-inch in diameter.
Slice dough every 1" to make the individual gnocchi.
Prepare well seasoned large cast iron skillet with 8 oz tomato sauce. On medium heat, add 8oz tomato sauce and 1 cup spinach. Once boiling, add gnocchi and cook for 6-8 minutes until firm yet tender. Check for internal temperature of 165'F.
Remove from heat, cool, serve, enjoy!