Set your Instant Pot to the high sauté setting and melt 2 tablespoons of unsalted butter. Once melted, add minced garlic and diced onion, sautéing for about 3-4 minutes until the onion is translucent and fragrant.

Add sliced cremini mushrooms to the pot, cooking for another 3-4 minutes until they are tender and have released their moisture. Season with a pinch of kosher salt and pepper.

Stir in arborio rice, ensuring it’s coated with the buttery mixture. Pour in the chicken broth and sprinkle in the dried thyme, then give everything a gentle stir. Close the lid securely and cook on high pressure for 6 minutes.

Once the cooking time is complete, perform a quick release of the pressure according to your Instant Pot’s instructions. Carefully open the lid when it's safe to do so.

Add the remaining butter and fresh baby spinach into the risotto. Stir thoroughly, letting the spinach wilt for about 2 minutes.

Mix in the thawed peas, gently folding them into the risotto for an additional minute until heated through. Optionally, stir in freshly grated Parmesan cheese.

Spoon the risotto into warm bowls and serve immediately for the best texture.