To a medium saucepan, set over medium heat, add the butter. Once it’s melted, it will begin to foam up and bubble a bit. Allow it to cook until you begin to see very lightly browned specks beginning to form. Add the walnuts; toss the walnuts until they’re evenly coated. Give it a stir and cook until it’s browned, about an additional 1 minute. Allow to stand until mostly room temperature.

Preheat the oven to 350 degrees F. Grease three 9-inch cake pans with cooking spray and set aside. I also like to line my cake pans with a sheet of parchment because I don’t like anything to stick!

In the a medium bowl, whisk together the flour, sugar, baking powder, baking soda and salt.

In the bowl of a stand-up mixer (or a large bowl using a stand-up mixer), whisk together oil and sugar, until combined about 1 minute. Then, add the reserved walnuts/brown butter mixture and beat for an additional minute. Add the eggs, along with the vanilla extract and mix until combined.

Add half of the dry ingredients and half of the milk and mix until incorporated. Add the remaining dry ingredients and the remaining milk; mix until smooth, about 30 seconds.

Divide the batter amongst the three pans (I only had two, so feel free to bake them in batches). If you want layers the same size, feel free to weight out the batter. Each layer will weigh about 345 grams. Smooth out the top using an offset spatula or butter knife. Transfer to the oven to bake for 20 to 25 minutes, or until a skewer comes out clean. Allow to cool in the pans for about 10 minutes and then invert it onto a cooling rack. Fill up the last cake pan and bake for 20 to 25 minutes, or until a skewer comes out clean.

To a bowl of a stand-up mixer with the paddle attachment (OR a medium bowl using an electric mixer), add the butter and vanilla. Beat until smooth and fluffy, about 30 seconds.

Sift in the powdered sugar. Cover the machine with a clean kitchen towel (this will avoid a mess) and turn it on low-speed. Increase the speed after about 30 seconds. Lastly, add the heavy cream and beat the frosting for about 2 minutes. The fluffiness from the heavy cream really lightens up this frosting so be sure to beat it for the full 2 minutes.

Pour all of the frosting on the cooled sheet cake and spread it around, creating cute swoops as you go. Top it with whatever you like! I added lil’ cookies. Cake will stay moist for about 3 days when wrapped properly.