First, prepare and cook the cassava. Cut it into chunks and peel it (read blog for more information!). Cut the pieces lengthwise to remove the root line inside the cassava (which will otherwise stay hard, and can’t be processed to a nice ball.)
Cook in boiling water until it is soft and fully cooked through, for 20 to 30 minutes.
In the meantime, take all the ingredients for the avocado filling and cut them into small pieces. Tip them to a medium bowl and add the oil, vinegar, chopped parsley, salt, and pepper to taste. I always add some lemon to the avocado so the color stays bright. Set aside.
Take the cassava out of the water and drain it properly so you don’t transfer any water to the bowl. Put the cassava in a large bowl and add the butter. Mash it with a potato masher until smooth.
Add the cornstarch, garlic powder, salt, and cilantro and mix everything together well, and start kneading it with your hands until it is well combined.
Scoop out a half cup of mixture and shape it into a ball. Make sure you create a big ball as you want them to have enough space for at least 1 tbsp of salad.
Beat the egg yolks together in a bowl. Tip the flour and breadcrumbs into separate bowls. Roll the cassava balls in the flour, then in the beaten egg yolk, and at the end, coat them with the breadcrumbs. Place them on a lined baking sheet. Refrigerate them all for 30 minutes.
Heat 2 to 3 cups of vegetable oil in a large pan, and once hot (be careful with hot oil), gently add the cassava balls and fry them until they become golden brown. Drain and transfer them to a plate lined with paper towels.
Allow the cassava balls to cool for a few minutes, then cut them in half and press down the middle of each half to make room for the salad filling.
Spoon 1 tbsp salad into the cassava cups, and decorate it with some beet sprouts.