Frozen Watermelon Slushie

Before you start

The trick to a slushie that tastes like watermelon rather than flavored ice is to freeze the fruit itself. Watermelon is mostly water, so frozen cubes act as the ice, and when they blend they keep every bit of flavor in the glass instead of diluting it. A squeeze of lime sharpens the sweetness and a tiny pinch of salt makes the melon taste riper.

The only real decision is texture. Blend straight from the freezer and you get a spoonable sorbet; let the cubes sit for five minutes or add a splash more juice and it becomes drinkable through a straw. Use the ripest melon you can find, because freezing mutes sweetness slightly.

Ingredients

• 700 g (about 5 cups) seedless watermelon — cut into 2.5 cm (1 inch) cubes, rind removed
• 15 ml (½ oz) fresh lime juice — about half a lime
• 60 to 90 ml (2 to 3 oz) watermelon juice or cold water — to help the blender move
• 1 to 2 tsp honey or sugar — optional, only if the melon is bland
• 1 small pinch fine salt
• 4 leaves fresh mint — optional

Method

1. Cut the watermelon into even 2.5 cm (1 inch) cubes, picking out any seeds. Reserve a few unfrozen cubes; you can blend them for the juice used later.
2. Spread the cubes in a single layer on a parchment-lined baking sheet so they do not freeze in a block. Freeze for at least 4 hours, until rock hard, then transfer to a freezer bag.
3. Let the frozen cubes rest at room temperature for 3 to 5 minutes. Slightly softened edges blend smoothly instead of spinning against the blade.
4. Add the lime juice, 60 ml of the watermelon juice or water, salt and mint to the blender, then the frozen cubes on top.
5. Blend on low, pressing the cubes down with the tamper, then increase to high for 20 to 30 seconds until thick and smooth. Add the remaining liquid a tablespoon at a time if it is too stiff to move.
6. Taste and blend in honey only if needed. Pour into chilled glasses and serve immediately with a spoon or wide straw.

Tips for success

• To make watermelon juice for the blending liquid, blend a handful of fresh cubes and strain them through a sieve.
• Frozen cubes keep well for about a month in a sealed bag, so you can freeze a whole melon at once when it is in season.
• If you do not have a tamper, stop the blender often and stir with a spatula rather than adding lots of liquid.

Substitutions

Lime juice

Lemon gives a softer tartness. A splash of tart cherry or cranberry juice deepens the color and adds tang.

Honey

Agave or simple syrup blend in easily. Skip sweetener completely with a peak-season melon.

Mint

Basil or a few slices of fresh ginger give a different herbal lift. A few frozen strawberries make it pinker and slightly thicker.

Variations

Strawberry watermelon

Replace a quarter of the melon with frozen strawberries.

Chili-lime

Rim the glasses with chili-lime seasoning and add a pinch of chili powder to the blender.

Troubleshooting

The slushie is watery

Too much liquid or the cubes were not fully frozen. Add more frozen cubes and blend briefly; start with less liquid next time.

The blender just spins

An air pocket has formed. Stop, push the cubes down to the blade, add a tablespoon of liquid and pulse.

It tastes flat

Freezing dulls sweetness. Add a little more lime and a pinch of salt before reaching for sugar.

The cubes froze into a single block

Drop the bag on the counter to break it up, or let it sit for 5 minutes and pry the pieces apart.

Storage

Serve immediately; it melts and separates within 15 minutes. Leftovers can be frozen in ice pop molds. Keep the unblended frozen cubes in a sealed bag in the freezer for up to about a month for best flavor.