Bird's Milk Cake: Russian Soufflé Cake with Agar-Agar
Ptichye Moloko, «bird's milk», is a Soviet soufflé cake: a thin sponge base, a tall layer of white foam that's light and creamy at once, and a chocolate glaze. The name is a Russian expression for something so exquisite it seems impossible. The cake version was created in the pastry kitchen of Moscow's Praga restaurant, the same house as Praga cake, and became so famous it was even patented.
The secret is agar-agar, not gelatin. The soufflé is built on an agar and sugar syrup cooked to 110 °C, like an Italian meringue. Agar gives it a firm yet airy texture that holds up outside the fridge. The flip side is that it sets at around 40 °C, so everything has to be ready before you pour in the syrup: once you start, there's no pausing.
🔎 What is agar-agar? — where it comes from, what goes in it and how it differs.
Ingredients
- 100 g butter, at room temperature (for the base)
- 100 g sugar (for the base)
- 2 eggs (for the base)
- 100 g all-purpose flour (for the base)
- 1 teaspoon vanilla extract (for the base)
- 4 g agar-agar powder (2 level teaspoons, for the soufflé)
- 150 ml water (for the soufflé)
- 300 g sugar (for the soufflé)
- 200 g butter, at room temperature (for the soufflé)
- 150 g sweetened condensed milk (for the soufflé)
- 4 egg whites (for the soufflé)
- ¼ teaspoon cream of tartar or a few drops of lemon juice (for the soufflé)
- 1 teaspoon vanilla extract (for the soufflé)
- 100 g dark chocolate (for the glaze)
- 50 g butter (for the glaze)
Method
- 1
Preheat the oven to 180 °C. Beat the butter with the sugar until creamy, add the eggs one at a time, then the vanilla and flour.
- 2
Spread the batter in a thin layer in a 22 cm springform pan lined with paper and bake for 12–15 minutes, until just golden. Let cool and leave it inside the ring, tightly closed, with a strip of acetate or parchment paper around the inside.
- 3
Before starting the soufflé, get everything within reach. Beat the butter with the condensed milk until pale and fluffy, and keep it at room temperature: if it's cold, the agar will seize into lumps when it touches it.
- 4
In a saucepan, mix the water with the agar-agar and bring to a boil, stirring. Let it boil for 2 minutes, add the sugar and cook without stirring until the syrup reaches 110 °C. You need a kitchen thermometer here: by eye it's very easy to overshoot.
- 5
While the syrup cooks, whisk the egg whites with the cream of tartar to soft peaks.
- 6
With the mixer running, pour the hot syrup in a thin stream onto the whites, down the side of the bowl and without hitting the beaters. Keep whisking for 2 minutes, until glossy and increased in volume.
- 7
Lower the speed and add the buttercream a spoonful at a time, then the vanilla. Work fast: as soon as it's combined, pour the soufflé over the base and smooth it. If you wait, it starts to set in the bowl.
- 8
Refrigerate for 2 hours, until the soufflé is firm.
- 9
For the glaze, melt the chocolate with the butter over a water bath and let it cool until it feels only barely warm. Pour it over the soufflé and spread into a thin layer. Refrigerate for another 2 hours before unmolding.
- 10
To slice, use a knife dipped in hot water and wiped dry, cleaning it between slices.