Preheat oven to 180C.
Into a bowl mix the dry ingredients: flour, potato starch, salt and baking soda. Blend together with a spoon so that its evenly mixed.
In another bowl, mix the oil, melted butter, sugar and blended cashews.
Add in the dry ingredients into the wet and mix thoroughly till combined. The dough should not be sticky and should be able to roll into a ball in the palm of your hand.
Lay out parchment over a baking tray and roll small 1-inch balls and place on tray. Next, press gently in the center with your thumb to make a small indent and place 1 piece of roasted cashew in the indent.
When all cookies are laid out, egg wash gently and then bake at 180C for 8 to 10 minutes, fan on.
Once the timer has sounded, turn off the oven and allow to bake with the residual heat for another 5 minutes.
Remove from oven and consume when cooled down as it will crisp up.