In a medium bowl, mix the feta with ½ teaspoon of the chilli flakes, 2 teaspoons of the fennel seeds and 1 tablespoon of the oil. Set aside while you cook the orzo.
Place a large sauté pan, for which you have a lid, on a medium high heat. Add 2 tablespoons of oil, orzo, ½ teaspoon of salt and a good grind of pepper. Fry for 3-4 minutes, stirring infrequently, until golden-brown, then remove from the pan and set aside.
Return the pan to the same heat and add the remaining 2 tablespoons of oil, 1 teaspoon of chilli flakes and 2 teaspoons of fennel seeds, the garlic and the orange skin. Fry for 1 minute, until the garlic starts to lightly brown, then add the tomatoes, stock, 200ml of water, ½ teaspoon of salt and plenty of pepper. Cook for 2-3 minutes, or until boiling, then stir in the fried orzo. Cover, then lower the heat to medium-low.
Leave to simmer for 15 minutes, stirring once or twice throughout so the orzo is cooked. Remove the lid and cook for a further 1-2 minutes, until the consistency is like a risotto. Stir in the prawns for 2-3 minutes until they are pink and cooked. Stir in the basil and serve at once, with the marinated feta sprinkled on top.
