Using the sauté function, melt 2 tablespoons of the butter in a 6-quart or larger pressure cooker.
Add the onion, garlic and ginger and sauté, stirring regularly until the onions begin to brown, about 4 minutes. Add the garam masala, coriander, turmeric and salt and cook until fragrant, about 1 minute more.
Add the tomatoes and their juices and stir to combine. Add the chicken breasts and make sure they are covered by the sauce. Seal the pressure cooker and make sure the vent is closed. Set the cooker to MANUAL, HIGH Pressure and dial down the time to 10 minutes.
The electric pressure cooker should take 10 to 12 minutes to come to pressure, then cook for 10 minutes. Let the cooker naturally release pressure for 10 minutes more.
Transfer the chicken breasts to a cutting board to cool slightly. Add the remaining 2 tablespoons butter and cream or coconut milk. Using an immersion blender, purée the sauce until smooth. (At this point, you can remove and reserve some of this incredible sauce for future use.).
Cut the chicken into 1-inch pieces, return to the butter sauce, and stir to combine.
Butter chicken is typically served over basmati rice, but brown rice, quinoa and cauliflower rice are wonderful alternatives.