• Bring a large pot of salted water to a boil. Rinse potatoes and add them to the pot (they do not need to be peeled). Cook until tender but still fairly firm (fork tender). Drain, cool, and put through a ricer (or mash). For best results, allow the potatoes to dry after ricing. Spread them out and let them dry for an hour or cover lightly and refrigerate overnight.

  *If you are wanting to make your gnocchi with the sauce-- prepare the sauce now (see below) and allow it to simmer on low while you prepare the gnocchi.
  
• Preheat oven to 400-degrees F.

  (Note: The next two steps can also be done in a stand mixer with the paddle attachment until mixed and then the dough hook until a dough forms.)

  Pour the flour our on a clean, lightly floured surface. Make a well in the flour and add 250 grams of the riced potato.
  
• Add the egg yolk, salt, pepper Grana Padano, and nutmeg.
  
• Using your hands, mix the ingredients together and then knead until combined and a dough ball forms. Shape small portions of the dough into "snakes". On a floured surface, cut snaked into half-inch pieces. Roll each piece by placing your finger at the top of each seam and rolling your finger down, forming a pocket. (Click on the video below to see how this is done)
  
• Roll around in the sieve until excess flour is removed and the dough has formed into pretty gnocchi ball.
  
• Place a square of mozzarella in each "pocket" and pinch shut. Sprinkle with flour and then place all of the dough balls in a sieve.
  
• Bring a large pot of salted water to a boil. Drop in all the gnocchi and boil until gnocchi has risen to the top (about 3-5 minutes).
  
• Drain and add to the sauce. Gently stir until well combined.
  
• Scoop the gnocchi into individual souffle dishes or into a small casserole dish if serving family-style. Add fresh basil, grana padano (or fresh parmesan) to taste. Cover with fresh mozzarella, hiding the basil under the mozzarella so the basil doesn't burn.
  
• Place in the oven on the top rack and bake for 12 minutes.

  Carefully remove from the oven and serve.
  

For The Tomato Sauce:

• Heat the olive oil in a deep skillet or sauce pan until hot. Add onion and stir until onion has lightly caramelized.

  Add the tomatoes and blend it all together using an immersion blender until smooth. Add salt, to taste. Keep adding salt until the acidity from the tomatoes has been mellowed out (about 3+ teaspoons).

  (If you don't have an immersion blender, combine the tomatoes, salt, and caramelized onion in a blender and puree. Return to the skillet to heat.)
  
• Allow to simmer on low, stirring occasionally, until ready to serve. Stir in fresh basil just a minute or two before serving.