Place a pot over low heat.
Pour in condensed milk, egg yolk, vanilla extract, a pinch of salt,mashed potato, & melted butter. Continue stirring until mixture is thick that can form into a ball. Turn off fire. Cool before wrapping.Once the mixture is cool get a spoonful of it & shape it into your desired shape either a pyramid or a ball shape. Roll over the sweet yema into a floured board to avoid sticking. Wrap yema in a colored cellophane.