Dice the onion, mince the garlic, and grate or finely chop the ginger; set aside.
Heat a tablespoon of oil in a skillet over medium heat until shimmering, then sauté the diced onion until translucent and fragrant, about 5 minutes.
Add the minced garlic and ginger to the skillet, cook for another minute until fragrant, and the mixture starts to sizzle.
Transfer the sautéed aromatics into your slow cooker, spreading them evenly at the bottom.
Rinse and chop the chicken thighs into bite-sized pieces, then add them to the slow cooker on top of the aromatics.
Pour in the diced tomatoes along with their juices, followed by the coconut milk, curry powder, salt, and black pepper. Mix everything well to coat the chicken evenly with the spices and liquids.
Cover the slow cooker with its lid and cook on low for about 6 hours, until the chicken is fork-tender and the sauce is rich and slightly thickened.
Once cooked, open the lid and give the curry a gentle stir. If the sauce is too thin, uncover and cook on high for an additional 30 minutes to reduce and thicken.
Taste the curry and adjust seasonings as needed—add more salt or a squeeze of lemon for brightness.
Spoon the fragrant, tender chicken curry over steamed rice or serve with warm naan bread. Garnish with fresh herbs if desired and enjoy the comforting aroma and rich flavors.
