In a 12 to 14-inch saute pan, heat 1/5 of the oil until just smoking. Saute each vegetable until tender and golden brown and remove each to a platter when finished cooking. To the pan, add vinegar, mint leaves, sugar and a pinch of hot chile flakes and stir with a wooden spoon over heat to dislodge the browned vegetable sugars in the pan. Pour the vinegar mixture over each of the 5 vegetables. Serve warm or at room temperature.