Set a 6-quart Instant Pot® to high saute and melt 4 tablespoons of the butter (see Cook's Note). Add the ginger, fenugreek leaves, fenugreek seeds, garam masala, garlic, cardamom, onion, serrano, cinnamon stick and 1 tablespoon salt and cook, stirring occasionally, until the onions are tender and beginning to brown, 8 to 10 minutes. Stir in the tomato paste and cook, stirring frequently and scraping the bottom of the pot so that it doesn't burn, until it turns a brick red. Deglaze with 3 cups water and stir to combine. Add the tomatoes and layer the chicken on top.
Follow the manufacturer's guide for locking the lid and preparing to cook. Set to pressure cook on high for 10 minutes.
After the pressure-cook cycle is complete, follow the manufacturer's guide for quick release and wait until the quick-release cycle is complete. Being careful of any remaining steam, unlock and remove the lid.
Remove the cinnamon stick and discard. Transfer the chicken to a plate, cover loosely with foil and set aside until ready to serve.
Set the pot to high saute and continue to cook the sauce, stirring occasionally, until reduced by half, 25 to 30 minutes. Turn off the pot and puree the sauce with an immersion blender. (Or transfer to a blender, let cool a few minutes and puree until completely smooth.) Add the cream and remaining 4 tablespoons butter and continue to blend until the butter is melted and the mixture is smooth and creamy and no streaks of cream remain.
Cut the chicken into 1-inch pieces and stir into the sauce. Let sit until heated through, about 5 minutes. Serve the chicken and sauce topped with cilantro over steamed basmati rice and naan alongside.
Settings may vary on your Instant Pot® depending on the model. Please refer to the manufacturer's guide.
When blending hot liquid, first let it cool for five minutes or so, then transfer it to a blender, filling only halfway. Put the lid on, leaving one corner open. Cover the lid with a kitchen towel to catch splatters, and pulse until smooth.
Copyright 2018 Television Food Network, G.P. All rights reserved.