Chopped parsley and finely grated Parmesan (for serving)
Set Instant Pot on medium heat or “Sauté” and pour oil into cooker insert. Add mushrooms and cook until any moisture they’ve released is evaporated and they start to brown, about 10 minutes; season with salt and pepper. Add onion, stir to combine, and cook until translucent, about 8 minutes. Add rice and stir until chalky white, about 3 minutes. Add wine and cook until mostly evaporated, about 3 minutes. Stir in stock. Lock on lid, making sure steam-release valve is in the proper sealed position. Select “Manual” and program for 5 minutes at high pressure (it will take about 10 minutes for the pressure to build before cooking automatically begins).
As soon as the time has elapsed, turn off cooker, “Quick Release” the steam, and unlock lid. Stir with a wooden spoon; season with salt and pepper.
Divide risotto among bowls. Top with parsley and Parmesan and serve.