Set Instant Pot to Saute. Add olive oil, butter, and mushrooms. Cook for 5-7 minutes, or until the mushrooms turn golden brown.
Add shallots and cook for 2-3 minutes, until shallots become translucent. Add arborio rice, garlic, and kosher salt. Cook for 1-2 minutes longer.
Deglaze the bottom of the instant pot with the white wine (optional) and/or chicken stock. Scrape the bottom using a wooden spoon, making sure any bits are removed. Secure the lid and cook at high pressure for 5 minutes.
Once the Instant Pot has finished cooking, release the steam manually until completely released. Remove lid carefully and stir in the parmesan and lemon juice.
Serve warm, with some fresh parmesan, freshly ground black pepper and any herbs and seasonings as desired.