Preheat the oven to 350 degrees F (180 degrees C) and line a baking tray with parchment paper.
Add flour and 1/2 cup icing sugar to a large mixing bowl. Whisk together, then add the vegan butter and combine it with the dry ingredients using a fork until thoroughly combined and a dough forms. Now add the vanilla extract and chopped walnuts, and mix together once more.
Shape the dough into 15 even-sized cookies (using around 1 1/2 tbsp dough per cookie) and lay them out on the baking tray. Bake in the preheated oven for 15 minutes, until crispy on the outside and a light golden color.
Immediately mix with the rest of the icing sugar, and serve.
Coat the cookies in icing sugar while they're still warm to ensure that it sticks.