Preheat oven to 400 degrees. Spray the inside of the tartlet molds with non-stick cooking spray. Set aside. My tartlet pan is made by Chicago Metallic and has four individual molds with removable bottoms in one pan. (see photo)

Melt the butter in a small saucepan over medium heat. When the butter begins to give off a nutty aroma remove from the heat. It took mine about 3 minutes and you will see specs of brown bits at this stage called beurre noisette.(hazelnut butter in French). Remove from the heat and set aside.

Lightly beat egg whites. Make a well in the center of the dry mixture and add the egg whites and the vanilla and whisk until fully combined. Slowly stir in the browned butter and whisk slowly to incorporate.

Pour the batter into each tartlet mold about 2/3 full. Bake for 7 minutes then open oven door and add 3 blackberries per cake and a little sprinkle of sliced almonds, close oven door and continue to bake for an additional 7-10 minutes or until the financiers are lightly browned at the edges and spring back in the middle. Let cool in the tartlet pan for 5 minutes before removing and placing on wire rack to fully cool. Repeat with remaining batter.

Sprinkle with confectioners sugar before serving and serve with additional berries if desired.