Step 1

Preheat the oven to 350° Fahrenheit. Grease a 9x13inch pan with butter or cooking spray. In a small bowl, whisk together the flour, baking powder, and salt, then set aside. Using an electric mixer, beat the plain egg whites in their own large bowl until soft peaks form. Add 1/2 cup of the sugar and continue to beat until stiff peaks form, then set aside. In a third, large bowl, beat together the butter, remaining 1/2 cup of sugar, egg yolks, and vanilla until lighter and fluffy. Add the dry ingredients into the egg yolk bowl and stir together until combined (it will be thick/stiffer). Using a spatula, stir in 1/3 of the stiff egg whites until the batter is smoother and easier to work with, then add in the remaining egg whites 1/3 at a time and fold in carefully.

Step 2

Pour batter into the prepared pan and smooth so that it covers the pan evenly. Bake for 20-30 minutes or until a knife inserted in the middle comes out clean. When the cake is done, let it cool completely before pouring the sauce mixture over it.

Step 3

While the cake is cooling, whisk together the sauce: the sweetened condensed milk, evaporated milk, and heavy cream. Once the cake is cool, use a long-pronged fork to poke holes all over the cake (the more the better!) so that the sauce can soak in. Pour the sauce over the cake and save about 1/2 cup in a container to add for plating (it will look like too much, but it will all soak in when left to sit in the fridge!). Chill the cake (covered) and the saved container of extra sauce in the fridge for at least 4 hours, and preferably overnight.

Step 4

Once the cake has chilled, before removing it from the fridge, beat the final topping together using an electric mixer. Beat the cream, powdered sugar and vanilla until stiff peaks form. Remove the cake from the fridge and, using a spatular or spoon, spread the whipped cream evenly over the top of the cake (it will form a 1/2-inch or more layer). Dust cinnamon over the top of the cake (optional, but great flavor!). And serve! We recommend using a large spatula to get the cake pieces out - they're a bit tricky!