Thạch Rau Câu, Vietnam’s beloved jelly (agar-agar) dessert, gets a fun twist with coffee and flan layers. Colorful, eye-catching, and surprisingly easy to make, it’s a treat that’s just as fun to eat as it is to look at.
What is Thạch Rau Câu?
If you’re in a hurry and just want to get cooking, feel free to jump into the recipe card.
In Vietnamese cuisine, Thạch Rau Câu (or simply Rau Câu) is a vegan-friendly jelly made from seaweed- and plant-based ingredients. There are actually two popular types of Rau Câu:
Both types of jelly are plant- and seaweed-based, making them vegan and ideal substitutes for gelatin. Depending on the recipe, Vietnamese cooks may use one type or even combine them to achieve the perfect texture for their jellies.
Ingredients
For Vietnamese, the coffee and flan combo is the ultimate treat! It’s no wonder this coffee-flan jelly is such a hit—Bánh Flan (Vietnamese flan) paired with strong Vietnamese coffee is already a beloved classic.
While some locals like to mix agar agar with konnyaku for a bouncier texture, I kept it simple with just agar agar, and it’s still incredibly tasty! With all the flavors in this recipe, there’s no need to complicate it further.
For a vegan version, you could replace the flan layers with coconut milk layers.
- Agar Agar Powder: Use brands from Southeast Asia, like Thai, Singaporean, or Vietnamese agar. Western brands often don’t yield the right texture in my experience.
- Granulated Sugar
- Salt: A pinch helps balance the flavors.
- Coffee Layers: I use instant coffee from Trung Nguyên, my favorite Vietnamese coffee brand.
- Flan Layers: Whole milk, sweetened condensed milk, egg yolk, Laughing Cow Cheese (or Cream Cheese, optional).
Instructions
Step 1 – Prepare the flan layer
- Lightly whisk the egg yolks in a bowl.
- In a separate bowl, soften the cheese with sweetened condensed milk. Add the whole milk and heat gently until just simmering.
- Slowly pour the warm milk mixture into the egg yolks, whisking continuously.
- Strain the mixture to remove lumps for a smooth texture.
- Cook over low heat, stirring constantly, until it begins to thicken. If curdled, strain again. Keep warm.
Step 2 – Prepare the coffee layer
- Brew the coffee and mix with hot water and sugar. Keep warm.
Step 3 – Prepare the agar agar mixture
- Soak agar agar powder in water for 30 minutes to 1 hour. Stir in sugar and a pinch of salt.
- Cook over medium heat, whisking constantly, until the agar agar totally dissolves and mixture boils. Keep warm.
- Split the agar agar mixture in half, stirring one into the coffee and the other into the flan. Keep both warm.
Step 4 – Assemble & Serve
- Pour the first coffee layer into your container and spread evenly. Let it cool slightly.
- Once set (won’t stick to your finger), gently pour a layer of flan mixture on top. Use a spatula under the spoon to prevent splashing and spread evenly.
- Repeat, alternating layers until all mixtures are used.
- Let the jelly cool completely, then refrigerate for a few hours before serving.
Helpful Tips
Making the layers stick together:
- Pour the next layer as soon as the previous one is just set on the surface (it shouldn’t stick to your finger but isn’t fully firm yet).
- The agar agar mixture should be very hot (you’ll see steam rising, but it shouldn’t be boiling).
- Or you can use a toothpick to lightly scratch the surface of the set layer before pouring the next one.
Your agar agar mixture has set: just add a few tablespoons of water and heat it over medium heat, stirring until it melts back into a smooth consistency.
For a firmer texture: In my recipe, the jelly has a softer, more delicate texture. If you prefer a firmer, crunchier jelly, just add a little more agar-agar powder to achieve the desired consistency.
Classic Vietnamese Desserts You’ll Love
(Bánh Bò Nướng Lá Dứa)
(Bánh Chuối Hấp)
(Bánh Khoai Mì Nướng)
(Sữa Chua)
Thạch Rau Câu Flan Cà Phê (Vietnamese Coffee Flan Jelly)
Ingredients
I recommend using a kitchen scale to measure these ingredients
Agar Agar Mixture
- 25 g agar agar powder (1 packet)
- 1500 ml water (~6.3 US cup)
- 300 g granulated sugar (~1½ US cup)
- ½ tsp salt
Flan Mixture
- ½ portion Agar Agar mixture (approx. 900 g or 750 ml, ~3.15 US cups)
- 5 egg yolks
- 175 g sweetened condensed milk (~¾ US cup)
- 7 pieces Laughing Cow Cheese (or 3.5 oz/100 g cream cheese, optional)
- 500 ml whole milk (~2.1 US cup)
Coffee Mixture
- ½ portion Agar Agar mixture (approx. 900 g or 750 ml, ~3.15 US cups)
- 500 ml coffee (made with 15 g or 0.5 oz instant coffee mixed with 500 ml, or 2.1 US cups, of water)
- 50 g granulated sugar (~⅓ US cup)
Instructions
Flan Layers
- Lightly whisk the egg yolks.
- In a separate bowl, soften the cheese by mixing it with the condensed milk. Add the whole milk and heat the mixture until it just begins to simmer.
- Slowly pour the warm milk mixture into the egg yolks, whisking continuously.
- Strain to remove any lumps for a silky texture.
- Cook the strained mixture over low heat, stirring constantly until it begins to thicken.
- If it curdles, simply strain it once more to achieve a smooth consistency.
Coffee Layers
- Brew the coffee, then add hot water and sugar. Mix well.
Agar Agar Mixture
- Soak the agar agar powder in water for 30 minutes to 1 hour.
- Stir in granulated sugar and a pinch of salt.
- Cook over medium heat, whisking constantly, until the mixture reaches a boil and the agar agar powder has fully dissolved.
Assemble & Enjoy
- Split the agar agar mixture into two equal portions: one for the coffee mixture and the other for the flan mixture. Keep both mixtures warm by either placing them on the stove on the lowest heat or using a hot water bath.
- Use the same cup to measure and pour each layer. The thicker the layer, the fewer layers you’ll have.
- Pour the first layer of coffee mixture into your container, spreading it evenly. Let it cool slightly (you can speed up the process by placing it in front of a fan).
- Once the coffee layer has set (it won’t stick to your finger when touched), gently pour the flan layer. You can place a spatula under the spoon to minimize splashing. Use the spoon to spread it evenly.
- Repeat the process with the remaining mixtures until all layers are poured.
- Let the agar agar cool and fully set, then place it in the fridge for a few hours to chill before serving.
Notes
- Pour the next layer as soon as the previous one has just set on the surface (it should not stick to your finger, but still be slightly soft).
- The agar agar mixture should be very hot (you’ll see steam rising, but it shouldn’t be boiling).
- Alternatively, you can gently scratch the surface of the set layer with a toothpick before pouring the next layer.
