Boil yuca: Peel and boil the cassava until it is tender, adding a tablespoon of salt to the water.Take out of the water and puree.
Mash yuca: Add the butter, parsley and milk and mix well.Season with salt to taste and let cool down to room temperature.
Make balls: Put two tablespoonfuls of the mixture in the palm of your hand. Flatten it, put a cheese cube in the center. and roll around it into a ball.Repeat with the remaining yuca mash.
Coat balls: Whisk the egg. Dip the balls into the egg, then into the flour. Coat it with flour and shake off the excess.Chill uncovered for 2-4 hours (you can keep them frozen in a lidded container for a couple of days).
Fry balls: Fry in medium-hot oil (350 ºF [175ºC) over until they are golden brown.Place on a paper towel to drain excess oil.
Serve: Preferably serve immediately while still warm.