Roughly chop the walnuts and then toast them in a dry frying pan for about 3-4 minutes of a medium-low heat and then set them aside and let them cool.
In a bowl mix together the almond flour, coconut flour, pumpkin spice and baking powder. Then add in the wet ingredients, the melted butter, vanilla, maple flavoured syrup and egg and mix well.
Add about 10grams of the walnuts to the batter and fold it in. Then pour into a mug or ramiken after lightly greasing it with butter.
Microwave at full power for 90 seconds. Cooking time will vary up or down by 30 seconds depending on the power of your microwave. What you can do is start with 60 seconds and then cook more if required. Obviously for a slightly more moist and gooey cake microwave it for about 10 seconds less.
Once the cake is cooked and has been cooled to room temperature just top it with the cream cheese frosting and finish by sprinkling those left over 5g of walnuts on top.