Preparation Fill a large bowl with ice water; set aside. Cook peas in a large pot of boiling salted water until crisp-tender, about 2 minutes. Drain; transfer to bowl with ice water to cool. Drain peas; transfer to a kitchen towel-lined baking sheet to dry. Whisk oil, 1 tablespoon lemon juice, vinegar, and 1/2 teaspoon sumac in a small bowl. Toss peas, radishes, and cheese in a large bowl. DO AHEAD: Can be made 1 day ahead. Cover dressing and salad separately and chill. Add dressing to salad and toss to coat. Season salad with salt, pepper, and more lemon juice, if desired. Garnish with mint and sprinkle with sumac.
Preparation Fill a large bowl with ice water; set aside. Cook peas in a large pot of boiling salted water until crisp-tender, about 2 minutes. Drain; transfer to bowl with ice water to cool. Drain peas; transfer to a kitchen towel-lined baking sheet to dry. Whisk oil, 1 tablespoon lemon juice, vinegar, and 1/2 teaspoon sumac in a small bowl. Toss peas, radishes, and cheese in a large bowl. DO AHEAD: Can be made 1 day ahead. Cover dressing and salad separately and chill. Add dressing to salad and toss to coat. Season salad with salt, pepper, and more lemon juice, if desired. Garnish with mint and sprinkle with sumac.