Bird's Milk is a dessert with Soviet roots that was popular in Belarus and across the entire Soviet Union. Its commercial production was patented in 1978. The cake is known for its delicate, almost weightless texture, which contrasts with the rich chocolate glaze.
Three things are key to preparation: agar-agar (gelatin must not be boiled), quality butter for the creamy base, and speed – the soufflé sets very quickly, so you need to work fast.
Preheat the oven to 185 °C (365 °F).
Cream the butter and sugar until fluffy. Add the egg and flour. Spread the batter onto the bottom of a 22 cm mold lined with baking paper.
Bake for 10-12 minutes until golden. Let the cake base cool in the mold. Line the sides of the mold with plastic wrap to prevent the soufflé from sticking.
Mix the agar-agar with 150 ml of water and let it swell for 10 minutes.
Whip the softened butter with condensed milk and vanilla extract until fluffy and creamy.
Bring the agar-agar to a boil and cook for 1 minute. Add the sugar and boil until the syrup thickens. Remove from heat.
Whip the egg whites with a pinch of salt until stiff peaks form.
Slowly pour the hot agar syrup in a thin stream into the whipping egg whites while continuously beating on low speed. Quickly switch to high speed and beat until the mixture thickens (soufflé).
Quickly (agar-agar sets fast!) add the butter mixture and mix only briefly until the components are combined. You must work quickly.
Immediately pour the soufflé onto the cooled cake base in the mold. Level the surface and refrigerate for at least 30 minutes until the mousse sets.
Melt the chocolate and butter in a water bath or microwave. Stir into a smooth, glossy glaze.
Pour the glaze evenly over the set soufflé. The cake must be completely cold.
Refrigerate the Bird's Milk cake for at least 3 hours, ideally overnight. Carefully release from the mold and remove the plastic wrap from the edges before serving.