Preheat the oven to 180C / 350 F and line two large baking sheets with non-stick baking or silicone paper.
Using an electric mixer with the paddle attachment beat the butter, cashew nut butter and sugar until well combined. Add the vanilla and egg and mix until creamy.
Remove the bowl from the mixer and sift in the flour, salt, baking powder and baking soda. Add the chopped nuts and then return to the mixer and briefly mix until it is thick dough and all ingredients are incorporated.
Scoop out tablespoons of dough and roll into balls. Toss these through extra sugar and place them on the baking tray allowing about 3cm (1.5 inches) space between each other. They will more or less double in size while baking.
Press down in a criss-cross pattern with a fork to flatten the cookie and leave a pretty pattern.
Bake for 10 minutes and until they just start turning a golden brown around the edges. Bake for a minute or two longer if you prefer them to be crispier.
Remove from the oven and try and allow them to cool completely before you eat them