Preheat oven to 200 degrees C/400 degrees F. In a large mixing bowl, stir together the gluten-free oats, baking soda, baking powder and ground flaxseed. In a separate mixing bowl, mix the maple syrup, peanut butter and plant based milk.
Combine the wet and dry ingredients, also adding the apple cider vinegar. Mix the dough using a spoon or your hands until well-combined. Then, form it into 10 even balls with damp hands and flatten them down on a non-stick baking sheet or baking paper. Bake in the oven for 10-15 minutes, until golden brown.
Meanwhile, make the frosting by adding the cashews, coconut milk and maple syrup to a food processor or blender and blending until very smooth.
Allow the cookies to cool down for at least 15 minutes, then spread on the cashew frosting and decorate with banana, dairy-free chocolate chips, red currants and dark chocolate. Serve straight away, or store in the fridge under cling film for up to 3 days.