Peel and chop the onion and dice t the bacon, and in the meantime turn the Instant Pot on and press the Sauté function key.Add olive oil, onion and bacon to the inner pot and cook for 5 minutes, stirring a few times, until golden brown.Add garlic, beef, salt, pepper, stock, red wine, tomatoes, and herbs and stir through. Add mushrooms, if using, and half of the carrots (reserve the other half for later). Press Keep Warm/Cancel to stop the Sauté function.Place the lid and lock. Set to Manual, High pressure, and set for 30 minutes. After three beeps the Instant Pot will begin to build up pressure and start cooking. Once the cooking finishes, release the pressure naturally for 10 minutes before using quick release to let off the rest of the steam.Add the remaining carrots and change back to the Sauté setting for a further 10 minutes (keep the lid off). Stir a few times. This process will thicken the sauce slightly by evaporating some of the liquid.Finally, combine the cornstarch or other flour with a couple of tablespoons or water or the broth from the stew in a small bowl, whisk together and return to the broth. Stir through immediately and then add the butter and stir through to finish the dish.Sprinkle with parsley when serving in bowls over your preferred side of vegetables or pasta.