Cook the onion and garlic in a skillet with 2 tablespoons olive oil. Add the spinach and heat through.
Boil the pasta in a large pot until al dente. Drain and return to the pot.
Put the egg yolks in a small bowl and whisk in a small amount of the sauce.
Mix the cheese and panko breadcrumbs together.
Work ¾ of the mixture into the spinach and noodles. Add the sauce and mix well. Pour into a casserole dish that has been prepared with a light coating of non-stick spray.
Top with remaining breadcrumbs and bake in a pre-heated 350 degree oven for about 20 minutes.
