In a large bowl, whisk together the sugars, bicarbonate of soda (baking soda), baking powder and salt.
Using a stand mixer or hand-held electric whisk, beat together the peanut butter and sugar mixture until fluffy. Add the egg and light miso. Continue to beat for about 30 seconds.
When ready to bake, preheat the oven to 180°C fan (350°F/Gas 4) and line a baking sheet with parchment.
Using an ice cream scoop or a tablespoon, scoop out mounds of dough onto the lined baking sheet, leaving about 4cm (1 1⁄2 in) between the cookies.
Bake in the preheated oven for 10–11 minutes, or until golden. Allow to cool on the baking sheet for 10 minutes before carefully transferring to a wire rack to cool completely.
ChillThe dough can be kept in the fridge in an airtight container for up to 10 days.FreezeShape the dough into mounds and open freeze. Once frozen, wrap airtight and freeze for up to 6 months.Bake from frozenPreheat the oven as above and bake the cookies on a lined baking sheet for about 10–11minutes, or until golden.