Switch on the instant pot to saute (normal) and melt butter + cooking oil. Add the onions and garlic. Saute until soft and fragrant (3-4 mins).
Add mushrooms, bouillon cube, curry powder, black pepper and salt. Cook until the mushrooms release water and become soft (4-5 mins).
Add all-purpose flour and vegetable broth. Mix everything well and cancel saute. Secure the lid and make sure the steam release handle is sealed. Hit the pressure cooking button (high) and set the timer to 4 minutes. When the pot beeps, wait for 10 minutes before releasing pressure.
Open the potand stir through the half and half cream. Add chopped parsley and serve hot.
Notes
If you are vegan, swap the half and half cream with 1 cup coconut milk or ½ cup coconut cream, and the butter for vegan butter or oil.
Instead of half and half cream, you can also use heavy cream. This will make the soup richer and heavier.
Use salt with caution as the broth and bouillon both have salt. The best advice here is to taste and go!
Use chicken broth instead of vegetable broth if vegetarian soup is not your thing.