Mix together the sugar snap peas, yoghurt, dill, ¼ teaspoon salt, ¼ teaspoon pepper, 2 tablespoons feta, and lemon juice in a bowl. Set aside.
Roughly mash the peas in a separate bowl and add the garlic, eggs, flour, lemon zest, breadcrumbs, and a little salt and pepper. Stir to combine.
Heat oil in a large saucepan. Using ¼ cup scoops of the pea mixture, form fritters and fry for 2–3 minutes on each side until golden and crisp. Drain on kitchen paper and season lightly with salt.
Toss the salad leaves, radishes, and cucumber with half the yoghurt-dill sauce.
Arrange the fritters on top, drizzle with the remaining dressing, and sprinkle over the extra feta.