Cook the pasta following pack instructions. Heat the olive oil in a pan then add the garlic and cook gently for 2-3 minutes. Tip in the tomatoes and harissa then cover and simmer for 15 minutes until thickened and saucy. Add the prawns and cook for 2-3 minutes or until pink then stir in a knob of butter, the basil and the orecchiette and season.
Spoon into warm bowls and add a spoonful of yogurt.