Drain and rinse cashews. Place all ingredients in a high speed blender, small strong food processor or smoothie maker with ice crushing blades and blitz til smooth and creamy. Chill.(icing will thicken once cold).
For the muffins
Preheat oven to 160 degrees C. Brush oil on the inside of patty cases so the muffins won’t stick.
Place all dry ingredients in a medium sized bowl. Mix well so the baking powder is distributed thoroughly.
Whisk wet ingredients together and add to dry. Mix till just combined.
Distribute evenly between patty cases and bake for up to 20 minutes or until an inserted skewer comes out slightly dirty.