Heat 4 tbsps olive oil in a large saucepan over a medium heat. Add the peppers, mushrooms, peas, green beans, cayenne, paprika, the juice of 1 lemon, garlic and a pinch of sea salt.
Cook for about 5 minutes until the vegetables are starting to soften then add the tomatoes and saffron. Cook for 2 minutes then stir in the rice, coconut milk and 200 ml water.
Cover and bring to the boil, then reduce the heat to very low and simmer for an hour, stirring every 20 minutes to make sure the rice doesnt stick.
After an hour the rice should feel cooked but al dente. Stir in the juice of the remaining 2 lemons.
Serve the paella in bowls with lemon wedges on the side and chopped coriander on top.