1/2 cup unsalted butter-melted and slightly cooled
1 Tablespoon water
2 cups milk-lukewarm
¾ cup sugar
2 tablespoons light brown sugar
1 cup flour
1 teaspoon vanilla extract
powdered sugar for dusting
Preheat the oven to 325°F. Lightly grease 8×8 inch baking dish, set aside (you can line it with parchment paper leaving the sides overhang the pan, it will be easier to serve, you can lift the cake and transfer plate).
Whip the egg whites until STIFF peaks form, set aside.
Beat the egg yolks and sugars until pale yellow.
Mix in melted butter and the tablespoon of water (for about 2 minutes) until evenly combined.
Mix in flour until evenly incorporated.
Slowly beat in the milk and vanilla extract until well combined.
Fold in the egg whites (1/3 at a time, then repeat until all of the egg whites are folded in). NOTES: The batter is very, very thin!!!
Pour the batter into the pan and bake for 45-60 minutes (until the cake is barely jiggly in the center). Baking time might vary depending on your oven or pan you use, but start checking after 45 minutes. If the top browns quickly before the minimum of 45 minutes, you can cover the cake with aluminum foil.
Cool the cake completely before dusting with powdered brown sugar. Even cooled, it will be slightly jiggly because it has custard layer in the center!