This is a recipe in the 4 Ingredients Allergy book. The original recipe calls for an avocado, 2 potatoes and olive oil. I substituted the potato with half a sweet potato (the orange kind) and half a kumera potato. I carefully diced the potatoes (all cubes the same size, very important), boiled them until slightly mushy, then added the ripe avocado and dash of oil as I mashed. I was surprised how good it was. Avocado is creamy, so it's almost like adding milk or cream to the mash but with a different flavour.
