In a bowl, mix the feta with ¼ tsp chilli flakes, 2 tsp fennel seeds and 3 tsp oil. Set aside while you cook the orzo. Place a large sauté pan that has a lid on medium-high heat. Add 30ml oil, orzo, a pinch of salt and a good grind of pepper. Fry for 3-4 minutes, stirring frequently, until golden-brown, then remove from the pan and set aside. Return the pan to the same heat and add the remaining oil, ¼ tsp chilli flakes and 2 tsp fennel seeds, the garlic and the orange peel. Fry for 1 minute or until the garlic starts to lightly brown, then add the tomatoes, stock, 200ml water, ¾ tsp salt and plenty of pepper. Bring to the boil, then stir in the fried orzo. Cover, lower the heat to medium-low and simmer for 15 minutes, stirring once or twice throughout, until the orzo is cooked. Remove the lid and cook for a further 1-2 minutes until the mixture has the consistency of risotto. Add the prawns and cook for 2-3 minutes until they’re pink. Stir in the basil and serve at once with the marinated feta sprinkled on top.