Pour Guinness into shallow pan and bring to boil on low heat. Reduce to have ¼ cup. For me, it took 13 minutes since the dish was quite large.

In a medium sized pan, combine heavy cream, corn starch and chocolate chips. Stir with spatula on low heat until chocolate is melted completely. Add reduced beer. Combine to have creamy texture.

Take away from the heat and add Oreo cookies powder. Incorporate well.

Cover tightly with transparent foil and cool completely. It needs about 2 -3 hours but I left it overnight in the fridge for the best results.

Pour cocoa powder into a shallow bowl.

Scoop little balls of cream using tea spoon.

Roll between palms to make it round and roll into cocoa powder.

Put each truffle on a tray and refrigerate until serving.