Preheat the oven to 350°F and position the rack in the middle of the oven. Prep a half sheet pan with a layer of parchment paper and lightly grease with nonstick cooking spray.

Cream together the butter and sugar with an electric mixer for at least 3 minutes on medium. Add the egg whites and vanilla, and beat well.

In a separate large bowl, stir together the dry ingredients: cake flour, baking soda, baking powder, and salt. Add the dry ingredients alternating with the milk to the mixing bowl, beating on medium speed. Scrape down the bowl and mix well. Pour the batter into the prepared half sheet pan.

Bake for 20-25 minutes or until lightly golden and a toothpick inserted in the center comes out clean. Allow to cool and cut out heart shapes with a heart-shaped cookie cutter.

In the bowl of an electric mixer fitted with the paddle attachment, beat butter for 2 minutes on medium speed. Adjust the speed to low and add powdered sugar, 1 cup at a time, until well incorporated.

Add salt, vanilla extract, almond extract, and heavy cream (or milk). Beat on medium speed for at least 3 minutes. Adjust frosting thickness as desired.

Fill a piping bag with frosting. Frost mini heart cakes and decorate with flowers and sprinkles.