In a pot on medium heat, add 2 tablespoons of vegetable oil and cook the onions until tender, add the minced garlic, grated ginger, and stir. Add 25 grams of butter, 1 tablespoon of garam masala spice, red chili flakes, cumin, dried coriander, hot red chili powder, salt, and pepper, and stir well. Add Knorr chicken stock cube and stir.
Add the mashed tomatoes, tomato paste, sugar, warm water, yogurt and let simmer for 10 minutes on low heat.
Season the chicken with salt, pepper, and the remaining tablespoon of garam masala spice.
In a separate pot, cook chicken in batches in the remaining 2 tablespoons of vegetable oil until tender and golden. (about 10 minutes)
Add chicken to the tomato/yogurt sauce and let boil for 5 minutes. Add fresh cream and let boil for another 2 to 3 minutes. Add the remaining butter, lemon juice, and cashews and stir well.
Transfer to a serving bowl and garnish with fresh coriander leaves, chopped green onions, and more cashews. Serve with basmati rice.