Mix the egg, butter, yeast, and sugar together, then add 1 cup (250 grams) of water.

Stir well until combined, then add the flour and mix with a whisk. Add the remaining 1/4 cup (50 grams) of water and continue mixing until the batter is smooth.

Cover the mixture and let it rise for 3 hours or until it doubles in size.

Bring a steamer to a boil. Grease flan molds with oil, fill them with the batter, and steam over high heat.

After 30 minutes, remove the cakes, let them cool, then take them out of the molds and serve.