Select the high Sauté setting on the Instant Pot and heat the ghee. Add the onion and cook until translucent, 4 to 5 minutes. Press the Cancel button to turn off the Instant Pot. Add the chicken, tomato puree, water, ginger, garlic, chile powder, salt, garam masala, and turmeric and stir to combine.
Secure the lid and set the Pressure Release to Sealing. Select the Poultry setting and set the cooking time for 13 minutes at high pressure. Let the pressure release naturally for 10 minutes, then move the Pressure Release to Venting to release any remaining steam. Open the pot. Allow chicken to cool down for a few minutes and then using a hand mixer shred the chicken. Note: You can also take the chicken breasts out and shred then using forks. Then return the shredded chicken back to the pot.
Add coconut cream, tomato paste, fenugreek, and sugar and stir to combine. Select the high Sauté setting and cook until the curry comes to a boil and is heated through, about 2 minutes. Press the Cancel button to turn off the Instant Pot.
To make the cucumber Raita, in a small bowl, add peeled and grated cucumbers and whisked yogurt. Stir in salt and ground cumin and garnish with cilantro.
Serve pulled butter chicken on brioche buns or rolls. Sprinkle with cilantro and serve with cucumber raita.