Cut your chicken into 1½ inch pieces and mix with the marinade ingredients. Allow this to marinate for at least 1 hour but ideally overnight.
Heat up a large pan over med-high heat to sear the chicken on each side. Don't worry about the chicken being cooked through as they will be added back later.
Remove chicken from the pan then add 1½ tbsp of butter with 1 tbsp oil into the pan along with your diced red onions. Stir to deglaze the pan for 1 minute.
Add minced ginger, minced garlic, ground cumin, garam masala, chili powder, and turmeric powder. Stir for additional 1 minute.
Add whole can of crushed tomatoes, cashews, and 1/2 cup of water. Cover to simmer another 15 minutes or until the cashews have been softened.
Place the sauce into a blender and blend until smooth. Make sure not to overfill the blender because the mixture is hot.
Once smooth, pour back in the pan with 2½ tbsp of butter, 1 cup heavy cream, chicken, and sugar. Mix then cover to simmer an additional 10 minutes or until chicken is fully cooked.
Serve with rice, garlic naan, and cilantro and yoghurt to garnish.