Prepare ingredients.

Cut open vanilla pod with a knife, carefully cut out black seeds inside, then cut into pieces and put them in a saucepan with milk.

Pour milk and 40g of sugar into a milk saucepan, turn on heat to low and bring milk to a slow boil, stirring gently with a spoon as it cooks.

Pour beaten egg yolk into milk in a thin stream, whisking constantly to drain milk so that yolk does not stick together, then place milk pot in a pot of cold water to cool.

Continue to simmer milk and egg yolk mixture over low heat until mixture thickens slightly.

Add sugar to condensed milk and beat until 6 points.

Pour chilled milk and egg yolk into condensed milk, mix well and freeze in refrigerator.

Remove frozen ice cream liquid every hour and mix once with an electric mixer. After mixing four times, it can be frozen.

When you're hungry, take it out of room temperature and let it sit for about 10 minutes, then scoop out balls.