Set the Instant Pot to sauté and add 1 tablespoon of oil. Once the oil has heated, add chicken in small batches, making sure not to crowd the pan. Cook until browned, about 2-3 minutes on each side. Set browned chicken to the side. Note- the chicken will not be fully cooked at this point. It will finish cooking while under pressure.
Add 1 tsp of oil to the pan, add the onions and cook for 3-5 minutes, stirring frequently while scraping up any browned bits stuck on the bottom of the pan, until the onions are translucent.
Add the garlic and ginger cook for about 30 seconds.
Add the spices (garam masala, cumin, turmeric, coriander, salt, chili powder, and cayenne pepper. Cook for 30 seconds until fragrant, stirring frequently.
Add the tomato sauce and chicken broth/water, stirring until all the spices have been incorporated.
Add chicken back into the pot and stir. Cover and cook on high ‘manual’ heat for 15 minutes. Quick release and open once the pressure cooker has depressurized.
Add cauliflower florets and give it a good stir. Seal and cook on high pressure (manual) for 2 minutes. Quick release and open once the pressure cooker has depressurized.
Stir in evaporated milk and arrowroot slurry (if using). To make the arrowroot slurry, in small bowl, combined 2 teaspoons of arrowroot powder with 2 teaspoons of water.
Top with fresh cilantro and serve on its own or with rice and/or naan.