Preheat your oven to 350°F (175°C). In a mixing bowl, whisk together the cake flour, baking powder, baking soda, and salt until well combined.

In a saucepan over medium heat, melt the unsalted butter until it turns a golden brown, about 5-7 minutes. Let it cool to room temperature.

Cream the cooled browned butter with sugar until light and fluffy. Add the egg whites one at a time, followed by sour cream and vanilla extract.

Gradually add the dry mixture to the wet ingredients, mixing on low speed, then stir in the whole milk.

Pour the batter into a lined 8x8 inch baking pan and bake for about 35 minutes, or until a toothpick comes out clean.

Allow the cake to cool completely in the pan on a wire rack.

For the frosting, beat unsalted butter until smooth, then add confectioners' sugar alternately with milk until fluffy. Add food coloring to achieve the desired color.

Spread the frosting on top of the cooled cake and add chocolate speckles for decoration.

Slice into squares and serve.