In a medium bowl, combine the flours, baking powder, ginger, and salt.
In a large bowl of a stand mixer, add the butter and sugars and beat until the mixture is very light and fluffy. Mix in the egg until incorporated. While the mixer is running, add in the dry ingredients and then the cream. Scrape down the sides of the bowl and beat in the mashed banana and vanilla. Fill each muffin cup 2/3 of the way with the batter.
Bake the muffins until toothpick inserted in the center comes out clean, about 15 minutes. Remove the tin from the oven and, when cool enough to handle, transfer the muffins to a cooling rack.
Brittle and caramel sauce:
Line a sheet pan with a silpat or aluminum foil that has been generously buttered.
Toss the macadamia nuts with the butter in a medium bowl.
In a heavy-bottomed saucepan, combine the sugar with the water and cream of tartar. Bring the mixture to a boil over medium-high heat. When the syrup reaches a medium golden-amber color, switch off the heat and stir half of the syrup into the bowl with the macadamia nuts. Pour the mixture onto the prepared sheet pan and let the brittle cool. To the remaining caramelized sugar, carefully stir in the coconut milk. Cool the sauce completely before using.
When the brittle has cooled, chop it roughly with a knife.
Arrange a pineapple ring on a small plate. Invert a cake onto the pineapple ring. Top with a small scoop of coconut ice cream and a sprinkling of the chopped macadamia brittle. Drizzle the dessert with 2 tablespoons of the caramel sauce and garnish with some mint. Repeat with remaining ingredients and serve.