In a medium sauce pan, cook the butter over medium heat. There's no need to stir. Let the butter melt and then cook. It will boil and then start to foam a little. Once you see the foamy layer, swirl the butter so you can see if it's turned a light brown and has brown specks in it. You'll be able to smell the brown butter as well. At this point, pour it into a liquid measuring cup and let it cool. You can do this step ahead of time and refrigerate the butter until you're ready to use it.

In a medium size bowl, whisk together the cake flour, baking powder and salt. Set aside.

In the bowl of a stand mixer, fitted with the paddle attachment, beat the brown butter, oil, and sugar on medium-high for about 3 minutes.

Add the eggs and the egg whites, one at a time, to the bowl and beat on medium until well incorporated.

Add the vanilla extract and beat on low until incorporated. Scrape down the sides of the bowl and mix on low for another 30 seconds.

Remove cakes from the oven and let cool in pans for 10 minutes before inverting onto cooling racks.

When cakes are completely cooled, I like to wrap each cake layer individually with plastic wrap and stick it in the refrigerator or freezer until I’m ready to frost. The cake will be easier to work with if it’s cooled a bit. If I’m making the cake a day or two before I actually need to frost it, I put it in the freezer to ensure freshness. If I’m frosting same-day, I’ll just put it in the refrigerator to chill until needed.

In the bowl of a standing mixer, whisk the eggs and salt until fluffy and frothy.

With the mixer on medium speed, add a tiny bit of the hot sugar mixture to the egg whites at a time. (Temper the eggs - don't scramble the them)

Eventually, all of the sugar will be added and then turn the mixer up to high. Beat the mixture on high for about 5 minutes or until very stiff and shiny.

Best used right away.

This step can be made ahead of time, but should not be added to the cake layers until the day you plan to serve the cake. The Rice Krispie Treats will soften and lose their crunch if you assemble this cake too early.

Spray a 9x13" pan with nonstick spray. Set aside.

In a microwave safe bowl, combine the butter and marshmallows and microwave for about one minute. You're looking for the marshmallows to get big and fluffy.

Stir the marshmallows and butter well.

Gradually add the cereal and stir to evenly coat the cereal with the marshmallows.

Pour and pat the cereal into the 9x13" pan. Let sit for several hours to harden.

In a medium saucepan, cook only 1 cup of the butter over medium heat. There's no need to stir. Let the butter melt and then cook. It will boil and then start to foam a little. Once you see the foamy layer, swirl the butter so you can see if it's turned a light brown and has brown specks in it. You'll be able to smell the brown butter as well. You'll want to do this step ahead of time and refrigerate the butter to get it back to a solid, cold consistency before you use it in the frosting.

In the bowl of a stand mixer fitted with the paddle attachment cream the one cup brown butter and the one cup of regular butter on medium speed for about 3 minutes, until the mixture is light and fluffy.

With the mixer on low speed, slowly add the powdered sugar, followed by the heavy cream, vanilla, and dash of salt.

Continue to beat the frosting on medium-high speed for an additional 5 minutes.

Before frosting your cake, mix the frosting by hand with a wooden spoon to push out the air pockets.