Cream the butter until light. Add the stevia or sugar and cream until almost white.
Add egg yolks one at a time, waiting for each to emulsify before adding the next.
Mix in the mashed bananas.
Mix the flours and the almond meal. Stir 1/3 of it into the mixture.
Add in 1/2 the coconut milk and another 1/3 of the flours. Mix.
Add the rest of the coconut milk and the flours. Mix well and set aside.