Penne with Swiss Chard and Sausage

I had never tried Swiss chard before this summer--it's definitely one of my favorite greens now. This dish is really quick to put together, and the flavors are great.

-2 T. olive oil
-2 cloves garlic, minced
-1/4 t. red pepper flakes
-1 small onion, finely chopped
-1 link chicken sausage, chopped
-1/2 lb. Swiss chard, stems removed and roughly chopped
-1/3 lb. penne
-1/4 c. freshly grated parmesan
-freshly grated salt and pepper

1. Cook the pasta in salted boiling water. Before draining, reserve 6 ounces of the pasta water.
2. In a large skillet, heat the oil over medium heat. Add the garlic, onion, and red pepper flakes, and cook about a minute.
3. Add sausage and cook thoroughly (if using pre-cooked sausage, cook until heated through and slightly browned). Add chard, and cook until leaves are wilted.
4. Toss sausage and chard with cooked pasta. Add the reserved pasta water, and stir in the grated parmesan. Season with salt and pepper. Garnish with additional cheese.