In a large mixing bowl, whisk together the non-dairy yogurt, ginger, garlic, lemon juice, spices, and salt until combined. Add 1 tbsp of water to thin out the marinade, if needed. Add the thawed chicken pieces and stir to fully coat the chicken in the marinade. Cover bowl and transfer to the fridge to marinate for at least 30 minutes, overnight is preferred. 

Heat 2 tbsp of olive oil in a large skillet. When sizzling, add chicken pieces and fry until browned for about 3 minutes on each side. Stir in 1 tbsp of vegan butter. Transfer chicken to a bowl and set aside. 

In the same pan, add sliced onion, soaked cashews, and chopped tomatoes. Bring to a low simmer and cook for 3-4 minutes until tomatoes have broken apart and onions are soft. Transfer to a high-speed blender and blend until smooth. Set onion-cashew-tomato mixture aside. 

Melt 2 tbsp of butter in the same pan. Add ground cumin, cardamom, cloves, coriander, sugar, turmeric, red pepper flakes, and cinnamon stick. Toast for 1 minute until fragrant, stirring constantly. Add grated ginger, minced garlic, tomato paste, garam masala, and 1 tsp of water. Stir well and cook for 1 minute.

Pour in the onion-cashew-tomato mixture, 1/2 cup coconut milk, and 1/2 cup water. Bring sauce to a simmer and cook for 5 minutes until it has slightly thickened. If your sauce is on the thicker side, add 1-2 tbsp of butter or a small amount of water and cook for an additional minute. Adjust taste with salt and pepper. Stir in 1 tbsp of butter. Add chicken and cook for 5 minutes. Remove cinnamon stick.

Remove from the heat and stir in chopped fresh cilantro. Serve Vegan Butter "Chicken" over rice and garnish with chopped cilantro. 

To store: Store in an airtight container in the fridge for 4-5 days or in the freezer for up to 3 months. Reheat butter chicken in the microwave or skillet.