Preheat the oven to 180°C (356°F).
Melt the butter that has been left at room temperature.
Sift almond flour, cake flour, sugar, and baking powder into a bowl.
Add the egg whites and mix well.
Add the melted butter and gently combine.
Cut the mango into small cubes.
Add the mango cubes to the batter and mix.
Fill the financier molds about 80% full with the batter.
Bake in the preheated oven at 180°C (356°F) for 15–18 minutes.
Let cool on a wire rack before serving.