Preheat the oven gas 6, 200˚C, 180˚C. Using scissors, cut the edge all the way around the pitta. Discard the edges and then cut the remaining pieces into large triangles. Pull them apart and arrange on 2 medium baking sheets or 1 big one. Drizzle with olive oil and salt and pepper. Bake for 7 minutes until golden and crisp. These can be stored in an airtight container for 2 days.
Mix the yogurt, radishes, mint and garlic together with some salt and pepper. Pour into a serving bowl and serve with the crisp flatbreads.