In a bowl, combine egg yolks and condensed milk. Stir together until well-blended.
In a non-stick pan over low heat, transfer egg and milk mixture. Cook, stirring regularly, until thick enough to form shape. Continuously scrape bottom and sides of pan to prevent burning.
Remove from heat and allow to cool. Shape into 1-inch balls.
In a pan, combine sugar, water, and vinegar. Stir until sugar is dissolved.
Bring to a boil. Cook until the liquid turns amber color, swirling the pan occasionally for even cooking.
Drop the custard balls one by one into the caramel and turn gently to coat. With a fork, immediately remove coated yema and place in a single layer on a non-stick baking sheet.
Allow to cool and wrap individually in cellophane.