Place the crushed garlic, peanut butter, coconut cream, chicken stock cube, boiling water, crushed ginger, soy sauce, mild curry powder, and brown sugar into the base of a slow cooker.
Stir the ingredients thoroughly until the marinade is well combined. The mixture does not need to be completely smooth at this stage, as it will blend further during cooking.
Add the sliced onion and sliced capsicum to the slow cooker.
Add the diced chicken breast or chicken thighs.
Stir until the chicken and vegetables are evenly coated in the satay sauce.
Cover the slow cooker with the lid.
Cook on high for 4 hours or on low for 7 hours, until the chicken is fully cooked and tender.
In a small bowl, combine the cornflour with 2 tablespoons of cold water.
Stir until a smooth slurry forms.
Add the cornflour slurry to the slow cooker about 20 minutes before serving.
Stir well to distribute the slurry evenly through the sauce.
Cover again and continue cooking until the sauce has thickened.
Taste the sauce and adjust seasoning if required.
Spoon the chicken satay over steamed rice.
Garnish with fresh coriander and sliced fresh chilli, if desired.
Serve immediately while hot.