This dish makes a simple but hearty weekday supper.
In a large sauté pan, add the oil and then sauté the onion over medium heat until it is translucent, about 5 minutes. Stir in the garlic and rosemary and sauté one minute more.
Add the rapini and beans, then add the vegetable stock and bring up to a simmer. Simmer uncovered for about 5 minutes, until the rapini is tender. Stir in the cooked pasta and return to a simmer. Stir in the walnut pieces and Balsamic vinegar and season to taste. Serve immediately.