- On a work surface, cut the rind off the melon. Cut the flesh into 18 perfect cubes. Place in an 8-inch (20 cm) square glass baking dish. Coarsely chop the watermelon scraps and place in a small pot.
- Add the chopped strawberries, sugar and water to the pot. Bring to a boil and simmer over medium heat for 5 minutes. Let cool completely at room temperature, about 1 hour. Strain through a sieve over the melon cubes. Let marinate for 1 hour at room temperature.
- Thread 1 strawberry half and 1 melon cube onto 18 short wooden skewers. Place on a serving dish. Drizzle with some of the fruit syrup and lime juice. Garnish with lemon balm leaves, if desired.
- Transfer the remaining fruit syrup to an airtight container. Cover and refrigerate. The fruit syrup will keep for 1 month in the refrigerator and can be served with grilled fruit salad, with ice cream, added to drinks – it adds a fruity kick to sangria – or to sweeten smoothies.