Ingredients For the Cake 3 2/3 cups cake flour 450g 2 1/4 cups granulated sugar 480g 2 tsp baking powder 2 tsp kosher salt 1.5 cups whole milk 355ml, room temperature 8 large egg whites room temperature 1 tbsp vanilla extract 15mL 17 tbsp unsalted butter 240g, room temperature 1/3 cup sour cream 80ml, room temperature
For the Milk Mixture: 3/4 cup whole milk 177ml 14 oz sweetened condensed milk 397g 12 fl oz evaporated milk 354mL
For the Frosting: 3 cups heavy whipping cream 710ml, cold, 1 cup confectioner's sugar 8 oz mascarpone cheese room temperature 1 tsp vanilla extract
For the Assembly: 9 strawberries hulled and sliced 1 sprig mint
Directions For the Cake: Preheat the oven to 350F. Prepare a 13" x 9" sheet cake pan by adding parchment paper. In a standing mixer, sift in the flour, baking powder, salt and sugar. Give it a whisk and set aside. In a large bowl, add egg whites, milk, vanilla, almond extract, and sour cream. Whisk together. Attach a paddle attachment to the stand mixer. Add in room temperature butter in cubes or pieces. On medium speed, beat for ½ of the wet mixture into the crumby dry mixture. Scrape the bowl down and add the remaining wet mixture. Beat until combined. Pour the batter into the prepared sheet cake pan. Bake for 30 - 35 minutes and/or until a toothpick inserted comes out clean. Let the cake cool to room temperature.
For the Syrup: Add the three milks into a large bowl, whisk together and set aside. You can add more milk to cut the sweetness if desired.
For the Frosting: In a stand mixer fitted with a whisk attachment, add heavy whipping cream, confectioners sugar. Beat on high until whipped. Add vanilla extract. Give it another whip on high. Fold in mascarpone by hand using a spatula. Switch to a whisk and beat.
For the Assembly: I trimmed the sides and top of the cake. You don't have to do this, but I wanted a nice fresh edge. Slowly drizzle on the tres leches on the cake. You can polk holed all over the cake to make more room for the sweet milk mixture if desired. Use an ice cream scooper to add the frosting. Smooth with an offset spatula. Garnish each piece with a fan of strawberry slices and a sprig of mint.