Melt butter in a pot. Add the condense milk. Stir and cook for about 3 minutes.
Add the egg yolks and continue to stir. Lower your heat and keep stirring until the whole thing thickens. About 15-20 minutes.
Transfer the yema into a bowl to cool completely. Stick the bowl in the fridge if you want to.
Chop about a handful of the chocolate chips. Once the yema is cooled, add the chopped chocolate chips. Mix the two together until well incorporated. Using a spoon, scoop up some of the yema and chocolate mixture, roll using the hands to create a mini-ball. Repeat with the rest of the yema-chocolate mixture. This recipe makes 20 balls.
FYI: It could get oily while rolling so just wash and dry your hands as you go along.
Store the yema balls in the fridge to set and firm up for an hour or 2.Melt the remaining half of the chocolate chips in a bowl using the microwave. About 1 minute and 30 seconds. Stir the melted chocolate until smooth. Roll the yema balls into the melted chocolate using a spoon. Repeat with the rest of chocolate chips to coat more yema balls. Set the coated yema balls into a platter to set for 5 to 10 minutes.
