In a pot, combine corn starch with 2 cups/500ml cold water, adding the water slowly
Stir over a medium-low heat and stir for a minute, then stir in the sugar. Stir for 10-15 minutes until the mixture thickens
Turn the heat to off and add the butter. Mix until completely dissolved, then turn to a low heat and stir in rose water, citric acid and vanillin
Mix for 5-7 minutes until the starch mixture becomes very thick. Set the starch mixture aside off of the stive and sprinkle shredded coconut onto a tray. If the starch mixture is still too runny, heat and stir for 2-3 minutes until thickened
Using a small ice cream scoop or spoon, scoop out a little of the starch mixture and press in one walnut half. Roll in the coconut and shape into a ball and repeat with the rest of the mixture. Refrigerate for an hour, then serve and enjoy!