For the gelato: Scoop the softened gelato onto a clean countertop or into a baking dish. Fold the blueberries, raspberries and mint into the gelato, using two rubber spatulas. Scoop into an airtight container and freeze for 2 hours.
For the macerated strawberries: Add the strawberries, vinegar, sugar, salt and pepper to a medium bowl, and toss to combine. Cover and leave for at least 20 minutes. Drain off excess liquid.
For the waffles: In a mixing bowl, whisk together the whole-wheat and all-purpose flours, the granulated and brown sugars, the baking powder and the salt. In a separate bowl, whisk together the melted butter, milk and eggs. Slowly pour the wet ingredients into the dry ingredients, mixing until just combined. Fold in half of the macerated strawberries. Cover and rest for 20 minutes.
Preheat a waffle iron and spray its surface with nonstick spray. Pour a generous 1/2 cup of the waffle batter into the iron, close and cook until golden brown, 5 to 6 minutes. Remove the waffle and repeat with the remaining batter, reapplying nonstick spray between waffles.
Place one perfectly cooked waffle on a plate and cut it in half diagonally to make two triangles. Top one triangle with a scoop of gelato. Sandwich with the other waffle triangle. Garnish with a spoonful of macerated strawberries, followed by a sprinkling of powdered sugar.