Chop up your spinach, mushrooms and peel and dice your onion.
Place the vegetables in the bottom of your Instant Pot.
Set the lid to sealing and cook on manual for 8 minutes.
Remove the vegetables once it beeps turning the valve straight away instead of leaving it to naturally release.
When the vegetables is cool enough to handle drain any liquid and make sure you have all excess water removed.
Place it into a bowl and crack the eggs into it and mix well. Add the rest of the ingredients and mix one last time.
Place grease proof paper around the sides of your spring form pan and then add the frittata mixture.
Place 200ml of water into the bottom of your Instant Pot, add the steaming shelf and place your spring form pan on top of this. Add the lid and set to sealing and cook on steam for 15 minutes.
When it beeps manually remove pressure, slice and serve.