Drain the artichoke hearts, reserving ¼ of the liquid. Add the artichoke hearts to your Instant Pot along with ¼ cup of the liquid. Then, add 3 cups of fresh spinach or 10 oz frozen spinach (no need to thaw).
Add 1 cup of sour cream, ¼ cup of mayonnaise, 8 oz of cream cheese, 4 cloves of garlic, ¼ teaspoon of salt, and ½ teaspoon of red pepper flakes on top of the artichokes and spinach in the Instant Pot. Do not add the other cheeses yet!
Close the lid, seal properly, by turning the pressure valve to the “Sealing” position, select “Pressure Cook” on “High” for 3 minutes.
When the timer is up and the dip has finished cooking, do a quick-release pressure setting carefully to open the lid.
Stir in 1 cup of cheddar, ½ cup each of mozzarella and parmesan and stir with a rubber spatula until it melts for about 2 minutes.
Press the "cancel" button if serving on a bowl, or "Keep Warm" mode to keep the cheese melted and free of lumps for a longer time.
Serve immediately, garnish with parsley, if desired.
