• Gather all ingredients before starting recipe.

Pasta

• Fill a medium large pot 2/3 full with water, add kosher salt, and bring to a boil. Add pasta shells, stir and reduce heat to a strong simmer and cook for about 15-20 minutes, or until shells are firm but cooked through. Drain, return pasta to cooking pot and add a little cold water to the pan to keep the pasta from sticking together. Stir the pasta to coat with water,

Filling

• Spoon ricotta cheese into a medium mixing bowl and add freshly grated parmesan cheese. Stir to combine and set aside until mushrooms are ready.
  
• Heat olive oil in a large skillet over medium heat, add sliced mushrooms and cook for 5-7 minutes, or until the mushrooms have released all their juices and begin to color. Season with kosher salt and black pepper.
  
• Add 1/2 cup of dry white wine, and cook until the wine has been reduced by half, another 5 minutes.
• Add fresh baby spinach, toss to combine and cook until the spinach has wilted and is completely combined with the mushrooms, 1 to 2 minutes.
  
• Allow the mushroom mixture to come to room temperature. Add mushrooms to ricotta mixture and stir to combine.
  

Sauce

• Add olive oil to the skillet used for the mushrooms and heat oil over medium heat. Add the chopped onions. Sauté until the onions become translucent, 5-7 minutes.
  
• Add the grated garlic and stir continuously for about 1 minute, pour in the marinara sauce, chopped tomatoes, and crushed basil. Stir to combine. Cover and simmer for 15-20 minutes to blend the flavors.
  

Assembly

• Remove sauce from heat. Remove one pasta shell from the water and fill the cooked shell with about a tablespoonful of filling. Place the filled shell on top of the sauce at the edge of the skillet. Keep filling and adding shells until you have enough shells to go all around the edge. Place a few shells in the center in a nice pattern. When all the shells have been added, re heat the sauce over medium heat until the sauce is bubbly and the pasta has been warmed through.