Razzleberry Crisp

To make the topping: Position a rack in the middle of the oven and preheat to 350 degrees F. Butter a 9-inch deep-dish pie plate. Stir together flour, sugar, salt, and mint with a fork, in a bowl, until completely blended. Add butter and work it in with your hands until it is the size of small peas; chill. To make the filling: Whisk together sugar, flour, and salt in a bowl. Add strawberries, raspberries, blueberries, blackberries, and apple and gently toss to coat. Pour fruit mixture into prepared pie plate and sprinkle with topping. Bake until fruit is bubbling and the top is golden brown and crispy, 50 to 55 minutes. Serve warm.