Lay watermelon cubes out on serving tray and top with feta squares.
Fold and skewer a mint leaf with a toothpick and then poke the toothpick through the feta and watermelon. Repeat for remaining cubes.
To make the balsamic glaze, heat vinegar and brown sugar over medium-high heat in a small sauce pan until it starts to simmer. Stir continuously while simmering for approximately 5 minutes until sauce has reduced almost in half.
Remove from heat and let sit for 1-2 minutes (do not let the glaze sit longer or it will become too thick).
Spoon a small amount of glaze over each prepared watermelon, feta, mint skewer and serve right away.
Notes
To make the recipe faster - buy store-bought balsamic glaze and use that instead of making your own. To prep ahead of time - watermelon and feta can be cut ahead of time and stored in separate tightly sealing containers in the refrigerator up to a day in advance. The skewers can be assembled an hour or two ahead of time but don't add the glaze until right before serving. Doubling Recipe - this amount makes 24 skewers and servings are listed as 4 per person. This is enough if serving other appetizers at a small dinner party but if you are not, you may want to plan for 6 per person. The recipe is easy to double if you have a larger group.