MELT butter in a 6 to 7-quart pressure cooker pot set over medium. Add onion and cook until soft, 2 to 3 min. Add rice. Stir until rice is glossy, about 30 sec. Add white wine. Stir until rice has absorbed all of the liquid, 1 to 2 min. Add vegetable broth.
COVER, and lock pressure cooker lid according to manufacturer’s instructions. Increase heat to high. When steam starts to come out of the vent pipe, reduce heat to medium.
COOK for 6 min. Remove from heat and let pressure drop naturally before unlocking lid. Stir in parmesan. Serve immediately.