With butter, grease a 1½-quart (1.5-L) casserole dish (I use one with a glass lid- see below in Recipe notes) that fits inside the Instant Pot. Set aside. In a large mixing bowl, whisk the eggs and cream together until the eggs are fully incorporated. Add the sea salt, raisins, lemon zest, ¾ of the cheese (reserving the rest for the top) and the mushroom-kale mixture, gently stirring to fully combine. Pour the mixture into a greased casserole dish. Evenly drop little dollops of ricotta into the custard filling. Place the glass lid on top of the casserole dish. Place the Instant Pot trivet inside the Instant Pot. Pour 1 cup (237 ml) of water into the Instant Pot. Carefully transfer the covered casserole dish to the Instant Pot on top of the trivet. Place the lid on the Instant Pot, making sure the steam release valve is sealed. Press the “Manual” setting and decrease the time using the “-” button until you reach 20 minutes.