Preheat oven to 350F. Prepare a 13x9 sheet cake pan with parchment paper.

Sift flour, baking powder, salt, and sugar into stand mixer.

In a bowl, whisk together egg whites, milk, vanilla, and sour cream.

Add room-temperature butter in cubes to dry mixture. Beat with paddle attachment.

Add half the wet mixture, scrape bowl, then add remaining wet mixture. Beat until combined.

Pour batter into pan and bake 30-35 minutes until toothpick comes out clean.

Let cake cool to room temperature.

Whisk together the three milks (whole milk, condensed milk, evaporated milk).

Poke holes in the cake and pour the milk mixture over it. Refrigerate.

Whip heavy cream with confectioners sugar and vanilla until stiff peaks.

Frost the cake and top with strawberries.