Heat the oil (or water) in a large soup pan that has a lid. (You will use it later.) Once hot add the onions and saute until translucent.
While the onions cook, make the blender sauce. Add the diced tomatoes, water, , cashews, ginger, garlic, garam masala, coriander, cumin, turmeric, and salt (if using). Blend until smooth. You may have to scrape down the sides of the blender a few times to make sure it's silky smooth.
Once the onion is translucent turn the heat to medium high and add in the butternut squash and the sauce. Once the sauce begins to simmer, cover and turn the heat to medium low. Cook for 20 t 30 minutes or until you can pierce the squash with a fork. You can add more water if the sauce gets too thick.
Add in the quartered Brussel sprouts and cook for 10 minutes or until the sprouts are tender.
Serve over Instant Pot Wheat Berries, steamed rice, or grain of your choice.
If you are making this with the Instant Pot Wheat Berries, start the wheat berries first and they should be ready to go once the curry is done.