Make Turkey Meatballs: In a large mixing bowl, place all the dry ingredients and mix in the wet ingredients. Use your hands to thoroughly mix the ground turkey mixture. Roll and form the meatballs. It yields 14 – 16 meatballs depending on the meatballs’ size.
Test Seasoning: Cook a small piece of turkey meatball mixture in a medium-high heat skillet and taste-test the seasoning. Add more kosher salt to the meatball mixture if it’s under-seasoned.
Brown Turkey Meatballs: Brown meatballs over medium-high heat in a skillet with 1 tbsp of olive oil. About 45 seconds - 1 minute per side until brown (See Notes).
Deglaze Skillet: Set aside the meatballs. Pour 100ml unsalted chicken stock. Scrub all the brown bits off the bottom of the skillet with a wooden spoon. Set aside and keep the brown bits (they are very flavorful).
Prepare Pressure Cooker: While you are browning the meatballs on the stovetop. Heat up your pressure cooker (Instant Pot: press Sauté button and click adjust button to go to Sauté More function). Make sure your pot is as hot as it can be (Instant Pot: wait until indicator says HOT).
Sauté Mushrooms: Pour 1 tbsp olive oil and 2 tbsp unsalted butter into your pressure cooker. Add in the chopped white or cremini mushrooms, a pinch of kosher salt and ground black pepper. Stir to evenly coat the mushrooms with butter. Mushrooms will start releasing their moisture. Let the moisture evaporate and stir occasionally until mushrooms are slightly crisp and browned. This step will take roughly 7 – 12 mins, but it will greatly enhance the flavor of the gravy.
Deglaze Pot: Add in the chopped shiitake mushrooms and give it a quick stir. Pour a dash of sherry wine and fully deglaze the pot with a wooden spoon. Now is a good time to add in the brown bits chicken stock liquid from the skillet. Pour in the remaining unsalted chicken stock and add 1 tsp of regular soy sauce.
Pressure Cook Turkey Meatballs: Add the turkey meatballs into the pressure cooker. Close the lid and cook at High Pressure for 5 - 6 minutes (depending on the size of the meatballs). Turn off the heat and do a Quick Release. Open the lid carefully. Make sure the turkey meatballs have reached 74°C (165°F) with a meat thermometer.
Make Mushroom Gravy: Taste the sauce and add salt if necessary. Mix 2 tbsp of cornstarch with 2 tbsp of water and stir the mixture into the mushroom gravy one third at a time until desired thickness.
Serve: Drizzle the mushroom gravy over mashed potatoes, pasta, rice, etc. and serve the turkey meatballs on top :)