In a medium-sized mixing bowl, whip egg whites at medium speed with an electric mixer fitted with the whisk attachment until soft peaks form.
Add 1/4 cup of sugar and continue whipping at high speed until stiff peaks form.
In another mixing bowl or the bowl of a stand mixer fitted with the paddle attachment, beat egg yolks and 3/4 cup sugar until pale yellow and doubled in volume.
Mix in milk, vanilla, cake flour, baking powder, and salt on low speed until fully combined.
Gently fold in beaten egg whites/sugar with a spatula.
Divide batter evenly between two 8" greased cake pans.
Add water to the bottom of the pressure cooker and place a trivet inside.
Place the first cake pan inside with a foil sling underneath it.
Close the lid and set the pressure release valve to locked.
If your pressure cooker has a cake button, press it to begin the cake cycle. Otherwise, cook at high pressure for 50 minutes.
When the cook cycle is complete, immediately power off and move the pressure release valve to its venting position.
When venting is complete, remove the cake pan using the foil sling and set it on cooling rack, leaving the cake in the pan.
Repeat with the second cake, making sure that about 1 1/2 cups of water remain in the bottom of the pressure cooker bowl.
Use a skewer or a toothpick to poke lots of holes in both cakes.
In a small mixing bowl, combine heavy whipping cream, sweetened condensed milk, and evaporated milk.
Pour liquid evenly over both cakes.
Cover both cake pans with plastic wrap and refrigerate overnight or for at least four hours.
Topping Instructions
Set the first cake onto a cake stand or decorative plate.
Use an offset spatula to spread whipped cream evenly over the top of the cake.
Place the second cake on top of the whipped cream.
To make the marshmallow frosting, combine egg whites, sugar, and vanilla in the metal mixing bowl of your stand mixer and set over a pot filled with boiling water on a range, creating a double boiler.
Whisk by hand for a few minutes until the mixture reaches 110 F on a candy thermometer.
Place the bowl on a stand mixer fitted with the whisk attachment. Whisk on medium speed for 10 minutes.
Increase to high speed and whisk until stiff glossy peaks form, about 5 to 10 minutes more.
Pipe on top of the cake.
Brown with a culinary torch.
Serve immediately or store in the refrigerator for up to three days.
Notes
Be sure to grease the pans well so that the cakes come out easily.
If there is any extra liquid that doesn't get absorbed into the cake, just drain the liquid into a glass and drink it!
If you prefer, you can make this cake as two single layer cakes.
If you don't have a pressure cooker, you can make this cake in the oven. Bake at 350 F for about 30 minutes.