Cook the pasta according to the package directions (boil for 7-10 minutes, or until al dente). Drain the pasta in a colander.
While the pasta is cooking, add the sausage links to a large pot along with one tablespoon of olive oil. Cook the sausage over medium heat for about five minutes, or until they are slightly browned and firm enough to slice.
While the sausage is cooking, mince the garlic and dice the onion. Remove the sausage from the pot and add the onion and garlic in its place. Sauté the onion and garlic in the pot for 2-3 minutes, allowing the moisture to dissolve the brown bits from the bottom of the pot. Meanwhile, slice the sausage into medallions. Once the onions are soft and transparent, add the sliced sausage back to the pot and cook for about 5 minutes more, or until the sausage is cooked through.
Add the can of crushed tomatoes, tomato paste, basil, salt, pepper, and brown sugar to the pot. Stir until the tomato paste is evenly combined with the tomato sauce.
By this time the pasta should be fully cooked and drained. Add the drained pasta to the pot, along with the frozen broccoli and spinach. Stir to combine. Heat the pasta and sauce over a medium flame until warmed through (stir occasionally to help it heat evenly). Crumble the feta into the pot, stir to combine, then serve.