Browned Butter Sheet Cake

Cake

1. Preheat the oven to 350 degrees Fahrenheit. Spray a 13x18x1 baking sheet with baking spray with flour in it, or use regular pan spray and dust generously with flour. Tap out the excess flour.
2. Add 1 cup unsalted butter to a small saucepan and melt it over medium heat until the butter browns, about 8-10 minutes. Watch for the butter to turn foamy and become very fragrant. It takes a while for it to start browning, but once it starts, it browns quickly, so don’t leave it unattended.
3. Once the butter is browned, carefully add 1 cup water to the butter in the pan and bring it to a boil.
4. While it comes to a boil, add 2 cups all-purpose flour and 2 cups granulated sugar to a large bowl and whisk to combine.
5. Add 2 large eggs, ½ cup sour cream, 1 tablespoon vanilla extract, 1 teaspoon baking powder, and 1 teaspoon salt and mix with a hand mixer on low speed.
6. Once the butter mixture is boiling, remove it from the heat and slowly mix it into the flour mixture. Scrape down the sides and bottom of the bowl to ensure everything is fully incorporated.
7. Pour the cake batter into the prepared pan and spread it out evenly. Bake for 25-27 minutes, until a toothpick comes out clean from the center and the top of the cake springs back when lightly pressed on with your fingers.
8. Let the cake cool completely.

Frosting

1. When the cake is fully cooled, prepare the frosting by adding 6 tablespoons unsalted butter to a medium saucepan and melting it over medium heat for about 6 minutes to brown the butter until the butter is foaming and smells nutty.
2. Turn off the heat and add in 6 cups powdered sugar, 1 teaspoon vanilla extract, and 8 tablespoons milk,. Mix until smooth. You can do this by hand, or you can use a hand mixer. The frosting should be thick enough to slightly hold its shape, but not stiff. If needed, mix in extra milk one tablespoon at a time.
3. Add the frosting to the top of the cooled cake and spread it evenly across. The frosting sets up quickly once it is finished, so you want to move quickly with this step.
4. Let the frosting finish setting up before slicing into pieces and serving.