Watermelon Agua Fresca

Method

1. 1Pick a good watermelon. This recipe lives or dies on the fruit. A ripe watermelon is deep red inside, not pale pink; it smells sweetly floral at the stem end; it feels heavy for its size; and when you tap it, it makes a hollow thud rather than a dense thunk. If the watermelon is not sweet, no amount of sugar will make the agua fresca taste like much. Cut the watermelon into rough cubes, removing the rind. You don't need to be precise — these are going into a blender.
2. 2Blend in batches. Working in batches if necessary, blend the watermelon cubes on high for 60 to 90 seconds until completely smooth and liquid. Add a splash of the water to help the blender if the watermelon is not releasing enough juice on its own. The blended mixture will look very pink and slightly foamy — the foam will settle. Do not add all the water at this stage; add only what the blender needs to run.
3. 3Strain and season. Pour the blended watermelon through a fine-mesh sieve into a large pitcher, pressing the pulp with the back of a spoon to extract maximum liquid. Discard the pulp, or skip this step entirely if you prefer a thicker, more smoothie-like texture. Add the remaining cold water, lime juice, lime zest, sugar or honey, and the pinch of salt. Stir well. Taste and adjust: more lime if it needs brightness, more sugar if the watermelon was bland, more water if it's too intense.
4. 4Add the mint and chill. Lightly bruise the mint leaves between your palms — just enough to release the oils without shredding them — and add to the pitcher. Let the agua fresca rest in the fridge for at least 20 minutes. The mint infuses gently and the flavors come together. Don't leave the mint longer than a couple of hours or it will start to taste slightly bitter and the color will darken.
5. 5Serve. Fill glasses with plenty of ice. Stir the pitcher well before pouring — watermelon agua fresca separates naturally as it sits, with the denser pulp settling at the bottom. Pour over the ice, add a mint sprig and a lime round to each glass. Serve immediately. The agua fresca keeps in the fridge for up to 2 days; stir before each serving.