Cut the grapefruit in half horizontally. Use a sharp paring knife to cut around each segment, inside the membranes, and around the inside of the pith. If the halves wobble, slice about ¼-½ inch off the bottom to create a base.
Sprinkle 1 tablespoon of the sugar over each grapefruit half. Use a small kitchen blow torch or the broiler to brown the sugar.
If using a torch, simply turn it on medium-high and evenly go around until all the sugar has caramelized.
If using the broiler, place the grapefruit halves on a baking sheet and adjust a rack so it’s directly under the flame. Broil the grapefruit just until the sugar has caramelized, about 1 minute. Watch it carefully as it can burn easily.
Garnish with mint and serve