Finely chop two of the onions and grate the remaining two. Heat the oil in a large pan. Add the garam masala and cook over a low heat, stirring constantly, for 1 minute. Add the chopped onions and cook for 10 minutes stirring occasionally. Stir in the grated onions, turmeric, cinnamon, cardamom pods chilli powder, cloves and bay leaves and cook, stirring constantly for 5 minutes. Stir in half the coconut milk and the algave nectar and season to taste with salt. Add the prawns and cook for 8 minutes, stirring frequently. Stir in the remaining coconut milk and bring to the boil. Adjust the seasoning if required. Serve with rice or salad.