In the bottom of the slow cooker, whisk together coconut milk, chicken stock, curry powder, salt and cayenne.
Add chicken breasts (see note), onion, chickpeas, tomatoes and sweet potatoes. Using tongs, gently toss ingredients together to ensure all are evenly coated.
Cook on medium setting for 7 hours or high for 3 1/2 hours.
Open the slow-cooker and remove the chicken. Once the chicken is cool enough to touch, cut it into bite-size chunks. Place chicken in the refrigerator until ready to return it to the pot.
Stir in peas and lemon juice and set the cooker for one more hour.
When the cooker is done, return the chicken to the curry and stir well to coat with sauce. At this point, I often keep the cooker on the warm setting while I'm getting the table ready so that the chicken warms completely.
Serve on its own as shown in my photos, or over rice, with plenty of fresh cilantro.