Rinse the spinach (do not dry) and place in a pot. Add salt and pepper. Cook over medium heat until tender, about 4-5 minutes.
Drain the spinach in a colander. Once it is sufficiently cool to handle, squeeze out as much water as possible.
Transfer the spinach to a cutting board and chop. Let cool to room temperature.
In a large bowl, combine spinach, garlic, ricotta cheese, flour, egg yolks and parmesan cheese. Taste and adjust seasonings.
Dust your hands in the flour. Take a small amount of the mixture and roll them into small balls in your hands.
Preheat oven to 350 degrees F. Lightly spray a 8x11-inch baking dish with no-stick cooking spray. Gently place them in the prepared baking dish. Place the baking dish on the middle rack of the oven and bake for 20-25 minutes. Transfer to a serving dish. You can serve gnocchi with melted butter and grated Parmesan cheese or any kind of sauce.