1. In a medium saucepan, warm the broth and the vanilla extract over medium-high heat.
2. When the broth comes to a simmer reduce the heat to low.
3. Add the butternut squash to the simmering broth and cook until tender, about 5 minutes. Using a slotted spoon remove the squash to a side dish. Turn the heat on the broth down to very low and cover to keep warm.
4. Meanwhile, in a large, heavy saucepan, melt 1 tablespoon of the butter over medium heat.
5. Add the onion and sauté until tender but not brown, about 3 minutes.
6. Add the rice and stir to coat with the butter.
7. Add the wine and simmer until the wine has almost completely evaporated, about 3 minutes.
8. Add ½ cup of the simmering broth and stir until almost completely absorbed, about 2 minutes.
9. Continue cooking the rice, adding the broth ¼ cup at a time, stirring constantly and allowing each addition to of the broth to absorb before adding the next, until the rice is tender but still firm to the bite and the mixture is creamy, about 20 minutes total.
10. Turn off the heat. Gently stir in the butternut squash, Parmesan, the remaining ½ tablespoon of butter, and salt.
11. Transfer the risotto to a serving bowl and sprinkle with chives. Serve immediately.
NOTE: If all the liquids are absorbed before the rice is tender but firm, add a bit more broth.