Heat 1 Tbsp of the butter in a large saucepan over medium heat. Add the onion and 3/4 tsp salt and cook, stirring often, until softened, 3 to 5 minutes. Add the rice and cook, stirring, for 30 seconds. Proceed to cook the rice according to package directions, replacing the water (if specified) with the equivalent amount of chicken broth.

Meanwhile, heat the oil in a large skillet over medium high heat. Add the mushrooms, 1/2 tsp salt and 1/4 tsp pepper. Cook, stirring occasionally, until browned, 6 to 8 minutes. Add the wine and cook, scraping up the brown bits, until evaporated, 1 to 2 minutes.

Fluff the rice and fold in the mushrooms and chives.

TO MAKE AHEAD: The pilaf can be made up to 2 days in advance; refrigerate, covered. Reheat before serving.