01 - Pat the cranberries dry thoroughly using a paper towel to eliminate excess moisture.
02 - In a medium-sized mixing bowl, whisk together the all-purpose flour, cornstarch, baking powder, and salt until well incorporated.
03 - In another bowl, lightly beat the egg and whisk in the ice-cold sparkling water until combined.
04 - Pour the wet mixture over the dry ingredients and gently stir just until incorporated. Do not overmix; slight lumps are acceptable.
05 - Pour vegetable oil into a deep saucepan or fryer to a 2-inch depth. Heat to 350°F, monitoring temperature with a kitchen thermometer.
06 - Working in small batches, dip cranberries into the tempura batter, ensuring each surface is well coated.
07 - Carefully lower battered cranberries into the hot oil using a slotted spoon. Fry for 1 to 2 minutes, turning as necessary until golden and crisp.
08 - Transfer fried cranberries to a plate lined with paper towels to drain and remove excess oil.
09 - If desired, dust with powdered sugar and sprinkle with freshly chopped mint. Present warm for optimal texture.