Preheat the oven to 110°C, gas mark ¼. Using a mandoline, thinly slice the radishes and place in a large bowl. Add vegetable oil and garlic powder to the radishes and season with the salt and pepper.
Toss to coat, then spread out in a single layer on 2-3 lined baking sheets. Bake until the chips are crisp and slightly golden – about 45 minutes.
Allow to cool for 5 minutes, then sprinkle with dukkah and serve.