Melt the butter.
Whisk the egg whites.
Mix the sugar, almond flour, and cake flour together.
Combine the melted butter with the mixed dry ingredients and blend well.
Finely chop the persimmon (use either ripe or firm persimmon).
Fill the financier molds about 2/3 full with the batter.
Place the chopped persimmon on top.
Bake at 180°C (356°F) for 15-20 minutes.