Rau câu: Vietnamese coconut jelly

Vietnamese coconut jelly, called rau câu dừa, is a firm, refreshing jelly made with agar, coconut water and coconut milk, usually set in two layers: one clear and one creamy white. It sets at room temperature and holds its shape well, so it's popular for parties, picnics and hot days.

What rau câu means

Rau câu (zow kow in the North, row kow in the South) literally means a kind of seaweed, the source of agar. In everyday speech, it's also the name for jelly made from agar. Dừa (zuh-uh or yuh-uh) means coconut. So rau câu dừa is coconut agar jelly.

Agar is different from gelatin. It's plant-based, it sets firmer and with a cleaner "snap," and it stays solid at room temperature, which makes sense in a tropical climate.

What you need

This makes about 6 cups (1.4 liters) of jelly, enough for an 8-inch (20 cm) square pan or a set of small cups.

• 2 teaspoons agar powder, divided (check your brand's package; see note below)
• 2 1/2 cups (600 ml) fresh coconut water, from 2 to 3 young coconuts or a carton
• 1 cup (240 ml) water
• 2/3 cup (130 g) sugar, divided
• 1 1/2 cups (360 ml) coconut milk
• 1/4 teaspoon salt
• 1 pandan leaf, knotted (optional)

A note on agar: agar powders vary in strength between brands. Follow the setting ratio on your package and adjust the amount for the total liquid. Agar flakes and strands need more and take longer to dissolve than powder.

How to make it

Clear coconut layer

• 1. In a saucepan, whisk 1 teaspoon agar powder into the coconut water and plain water while cold. Let it sit 5 minutes.
• 2. Add 1/3 cup of the sugar and the pandan leaf. Bring to a boil over medium heat, stirring.
• 3. Boil gently for 2 minutes, stirring, so the agar fully dissolves. Agar has to boil to set; just warming it isn't enough.
• 4. Remove the pandan leaf and pour into your pan or cups. Let it sit 10 to 15 minutes, until the surface is set but still slightly tacky.

Creamy coconut milk layer

• 5. In a clean saucepan, whisk the remaining agar into the coconut milk, salt and remaining sugar.
• 6. Bring to a gentle boil, stirring constantly so the coconut milk doesn't scorch or split. Simmer 1 to 2 minutes.
• 7. Using a fork, lightly scratch the surface of the first layer, then gently pour the coconut milk layer over it. Pouring over the back of a spoon helps.

Set and chill

• 8. Let it set at room temperature for about 30 minutes, then chill at least 2 hours.
• 9. Cut into squares or diamonds, or unmold the cups.

Getting the layers to stick

The trick with layered agar jelly is timing. If the first layer is fully cold and firm, the next layer won't bond and the two can slide apart. If it's too liquid, the layers blend. Pour the next layer when the first has just set on top. Scratching the surface lightly also helps them grip.

Serving it in a coconut

A classic presentation is jelly set inside the coconut shell itself, sometimes called rau câu trái dừa. You drain a young coconut, fill it with the coconut-milk mixture or coconut-water mixture, chill it, and slice it into wedges. The tender coconut meat lines the edges of each piece. It takes some knife work to open the coconut safely, so a store-bought coconut with a pre-scored top makes it easier.

Variations

• Coffee layer: swap the clear layer for sweetened brewed Vietnamese coffee. See how to make Vietnamese coffee at home.
• Pandan layer: add pandan juice to a coconut milk layer for green and white stripes.
• Rainbow layers: alternate several colors, letting each set before the next.
• Fruit pieces: add diced mango, lychee or jackfruit to the clear layer.

Storage and allergens

Keep it covered in the fridge for up to 3 days. It may weep a little liquid over time; that's normal for agar.

This jelly is vegan, gelatin-free and naturally gluten-free. It contains coconut. There are no nuts, dairy or eggs.

Where it fits

Rau câu sits alongside other Vietnamese sweets at family gatherings and parties. For more, see Vietnamese desserts to know and try and bánh flan, Vietnamese caramel custard.

Boil the agar fully and pour the second layer while the first is just set, and you'll get clean, tidy stripes.