Heat the oil in a medium to large pot and add the sausage. Break the sausage apart as it browns in the pan. Once the sausage is cooked, add in the penne and just enough water to barely cover it.
Bring it up to a boil and mix frequently to cook the pasta. Keep mixing and adding a splash of water as needed until the pasta is al dente. This should take around 10 to 15 minutes and when it's done, there shouldn't be a lot of liquid left in the pot.
Once the pasta is cooked, turn the heat to low and mix in a handful of spinach. Then pour in the pasta sauce (only use ½ the jar) and mix well. Cook for another minute or two mixing frequently. Remove from the heat. Top with shredded parmesan cheese and serve!
