Preheat oven to 350 degrees F (175 degrees C). Bring a large pot of lightly salted water to a boil. Add pasta and cook for 8 to 12 minutes or until al dente; drain.

Heat oil in a large, deep skillet. Place sausage and onion in the skillet and cook over medium high heat until evenly brown.

Drain excess fat. Pour in chicken stock, and cook for 1 minute, stirring, to deglaze the pan. Stir in marinara sauce.  

Simmer for 5 minutes, stirring occasionally. Toss with cooked pasta, and place in a 9x13 inch baking dish. Sprinkle top with mozzarella.

1 cup serving size