Bring a kettle of water to a boil. Place the cashews in a bowl and add enough boiling water to cover. Soak for 30 minutes.
Heat 2 tablespoons of the ghee in an Instant Pot using the Sauté setting. Add the chicken, shallots, and onion and sauté for 8 minutes, until the chicken is browned and the onion is translucent. Add the remaining 4 tablespoons ghee, the tomato puree, tomato paste, lemon juice, garlic, cardamom, cinnamon stick, bay leaves, ginger, garam masala, cumin, salt, turmeric, and fenugreek and stir to combine. Secure the lid and select the meat/stew setting, or select the Pressure Cook and Manual setting and cook at high pressure for 10 minutes.
Meanwhile, drain the cashews, rinse, and drain again. Combine the cashews and 3/4 cup water in a blender. Blend on high speed until very smooth and creamy, about 30 seconds in a high-speed blender, or 1 minute in a conventional blender.
When the Instant Pot timer is done, quick release the pressure and stir in the cashew cream. Spoon the butter chicken into serving bowls. Sprinkle with almonds and cilantro and serve with naan on the side.