- Press the Saute button on the Instant Pot. Warm the olive oil, then add onion, carrot, celery and garlic. Saute 3 to 5 minutes.
- Add half of the mushrooms and mix well into the onion mixture. Make sure to scrape the bottom of the pot, loosening any bits of onion that have stuck.
- When the mushrooms have wilted and cooked down a little (2 minutes) add the remaining mushrooms and saute about 3 minutes more, stirring occasionally, until all of the mushrooms are soft. Season with salt and pepper.
- Add balsamic vinegar, tomato sauce, water, lentils, salt, oregano and bay leaf. Mix well.
- Secure the lid. Make sure the steam release valve is in the sealed position. Cook on high pressure for 15 minutes.
- When the cooking time is complete, let the Instant Pot release pressure naturally (this will take 15 to 20 minutes).
- Mix well, add salt to taste. Make sure to add fresh basil and grated cheese before serving.
Recipe Note: The lentil bolognese might seem watery at first, but this is fine - you don’t want the sauce too thick or it won’t blend well into pasta. Also, as the sauce sits the lentils will continue to absorb some of the water and the sauce will thicken, especially if kept a day or two in the refrigerator. However, if you prefer a thicker sauce, you can simmer the sauce after it cooks to thicken it up.