Preheat the oven to 375° F. Grease 2 quart or 13" x 9" baking dish. Set aside.
Bring a medium pot of water to a boil. Cook gnocchi in water for 2 minutes. Remove and set aside.
In a large skillet, heat up olive oil.
Add onion and saute until almost translucent.
Add garlic and saute for 2 minutes, stirring often.
Add Italian sausage and cook until brown, then 4 to 5 minutes longer OR until darker brown bits form at the bottom of the pan (you want the Maillard reaction) which will add even more flavor.
Add Italian seasoning and crushed tomatoes. Season sauce with salt and pepper. Stir everything together and bring to a simmer.
Add gnocchi and stir with the sauce. Remove from heat and pour into prepared baking dish.
Top gnocchi with cheese and bake in the oven for 20 minutes OR until bubbly along the edges and the cheese is melted.
Remove from oven, let cool for 10 minutes, then serve. Garnish with fresh basil or Italian parsley.