2. Pour the milk into a small pot and heat it on a small fire until it bubbles from the fire. Pour in oil, stir until there is no oil star, and emulsify evenly.

3. Pour in the pre-screened flour and stir until there is no dry powder. Let the batter cool a little, then pour in the egg yolk and stir well.

4. Add salt to the protein and stir until the protein thickens. Add sugar to the egg whites in three times, and beat until the egg milk is upright.

5. Take 1/3 beaten egg white cream and mix well.

6. Pour into a 6-inch mold, shake out bubbles on the table, cover the mold with a dish or plastic wrap, put it in a steamer with boiling water, and steam for about 40-50 minutes on medium heat.