1. Prepare the Watermelon: Start by cutting your seedless watermelon into 1-inch cubes. Lay the cubes in a single layer on a baking sheet lined with parchment paper. This prevents them from sticking together as they freeze. Place the baking sheet in the freezer for at least 4 hours, or preferably overnight, until the watermelon is solid. This is the most important step for achieving a thick, icy slush.

2. Gather Your Ingredients: Once the watermelon is frozen, retrieve it from the freezer. Have your fresh mint leaves, lime juice, optional sweetener, and cold water ready.

3. Add to Blender: Carefully transfer the frozen watermelon cubes into a high-speed blender. Add the fresh mint leaves, fresh lime juice, and your chosen sweetener (if using).

4. Start Blending: Pour in 1/4 cup of cold water. Begin blending on a low speed, using the tamper if your blender has one, to push the ingredients down towards the blades. The mixture will be very thick at first.

5. Achieve Slushy Consistency: Gradually increase the blender speed. If the mixture is too thick to blend smoothly, add cold water one tablespoon at a time, blending after each addition, until you reach your desired slushy consistency. Be careful not to add too much water, or your slush will become too thin. You’re looking for a thick, icy, spoonable texture.

6. Taste and Adjust: Once blended, taste the slush. If you prefer it sweeter, add a little more honey or maple syrup and blend again briefly. If it needs more zing, a tiny squeeze of extra lime juice can perk it up.

7. Serve Immediately: Pour the watermelon mint slush into chilled glasses. Garnish with a fresh sprig of mint or a small wedge of lime on the rim of the glass for an extra touch of elegance.

8. Enjoy: Serve immediately and savor this wonderfully refreshing homemade treat!