Mist a pan with spray oil. Add the onion and cook for 5 minutes until softened and brown. Add the garlic, ginger, scotch bonnet and allspice and cook for 1-2 minutes, until fragrant. Add the coconut milk and bring to a simmer.
Meanwhile, mist a wide pan with spray oil over a high heat and brown the plantains for 1 minute on each side.
Transfer the plantain and coconut mixture to the slow cooker with the black beans, peppers, thyme and a splash of water. Put on a high heat for 1 hour, then add the spinach and cook for a further 1 hour until the sauce has thickened and the plantain and peppers are tender. Serve sprinkled with coriander.