In a small mixing bowl, add the almond flour, coconut flour, brown sugar, baking powder, ginger, allspice, cinnamon, egg, and milk and mix well. If the batter is too thick, add extra milk.
Grease a microwave-safe mug or bowl generously and pour the batter into it, and microwave for 1 minute. If the cake is very undercooked, microwave it in 20-second bursts until done. If not, let it sit for a couple of minutes.
Oven option
Follow as above, but bake in an oven safe dish at 180C/350F for 10 minutes.