Turn the sauté function on the Instant Pot and wait for it to heat up. (You don't need to put the lid on or bring it to pressure).
Once it's hot, add a small amount of oil to the pot and add 1 cup of diced white onions.
Stir the onions around and cook until they become translucent.
When the onions are cooked, add all of the frozen broccoli and stir.
Add one cup of vegetable broth.
Close the Instant Pot lid and use the pressure cook function for 5 minutes with the vent on sealing.
Once the 5 minutes are up, release the pressure by turning the valve to venting and vent until the pin drops, then press cancel.
Remove the lid and stir the broccoli.
Add another 1 cup of vegetable broth as well as 1 cup of orzo.
Close the lid and bring the Instant Pot back to pressure cook.
Cook for 3 minutes before releasing the vent again.
After releasing the vent, remove the lid once the pressure pin drops.
Stir the orzo with the broccoli and ensure that it is fully cooked.
Press 'cancel' to turn off the pressure cook function.
Press the 'keep warm' button.
Sprinkle in 1 tablespoon of flour and stir, ensuring no clumps.
Make sure the flour is fully combined, then add ¼ cup of nutritional yeast and combine.
Next, add 1 can of unsweetened coconut milk to the pot and stir to combine.
Then, add ½ tablespoon of salt and of garlic powder.
If you have it, add the vegan cheddar and mix until melted.
Continue stirring until the soup is fully warm.
Taste the soup and add more salt if needed.
Scoop the soup out into bowls and garnish with scallions and more vegan cheddar.