Start by heating a sauté pan over medium heat and add a tablespoon of oil. Toast the garam masala, cumin, and coriander for about 1-2 minutes until fragrant and slightly darker, then remove from heat and set aside.
Add the diced onions to the slow cooker, then pour in the coconut milk. Mix gently to combine the aromatics with the creamy base.
Place the chicken thighs into the slow cooker, then sprinkle with the toasted spices, turmeric, and a pinch of salt. Toss everything gently to coat the chicken evenly in the fragrant mixture.
Cover the slow cooker and cook on low for 6 to 8 hours, or on high for 4 to 5 hours, until the chicken is tender and falling apart. Avoid opening the lid during the first few hours to keep the heat steady.
About 30 minutes before finishing, stir in the toasted almonds or cashews for added texture and flavor, allowing them to warm through.
Once cooked, the chicken should be tender and easily shredded. The sauce will be rich, creamy, and fragrant with spices and coconut aroma.
Turn off the slow cooker, let the curry rest for 10 minutes to deepen the flavors, then taste and adjust seasoning if needed. Serve hot over rice or with naan, garnished with fresh herbs if desired.
