In a large bowl, mix the cut chicken thighs with the Aleppo pepper, garlic cloves, ginger, curry powder, turmeric, and yogurt until well combined. Lightly season with salt and pepper. Set aside and allow to marinate for at least 30 minutes on the countertop or for up to 8 hours in the fridge.
In a large non-stick skillet over medium-high heat, sear the chicken on each side until browned on each side, about 2-3 minutes. Do not cook completely or overcrowd the pan. This may have to be done in batches. Set aside, leaving any drippings in the pan.
Add in 1 Tablespoon of the butter to the pan, followed by the onions. Cook for 3-5 minutes, or until translucent.
Stir in the berbere seasoning and tomato paste. Cook for another minute.
Carefully stir in the chicken stock, scraping off any burnt bits at the bottom of the pan.
Add the chicken back into the pan and bring to a boil. Once bubbles form along the surface, reduce the heat to low and cover the pan with a lid.
Simmer for 15 minutes, stirring occasionally.
Slowly add in the heavy cream and cook for an additional 10 minutes. The sauce will become thick and creamy.
Season with salt and pepper if needed.
Garnish with cilantro and serve over freshly steamed rice and with warm bread.