This brown butter chocolate chip cookie cake is a riff off of the childhood classic with a gooey texture, notes of caramelized butter, and a variety of chocolate chips!
Add parchment paper to the bottom of a 9" springform pan.
Brown the butter: In a small saucepan, add 204g (14 ½ tbsp) of unsalted butter and place over medium heat. As the butter melts, stir it with a rubber spatula to encourage even cooking. Once the butter has fully melted, it will alternate between rapid large bubbles and gentle small foamy bubbles. The butter will be ready once it turns a dark golden color and the fat solids have darkened and settled at the bottom of the pan. Immediately pour into a large bowl, scraping out the fat solids at the bottom, and weigh out to 170g (¾ cup). Set aside to cool for a few minutes.
Meanwhile, in a medium bowl, whisk together the flour and baking powder. Set aside.
To the brown butter, whisk in the sugars and salt until fully combined. Then, mix in the eggs, egg yolk, and vanilla.
Add in the dry ingredients, and gently fold with a rubber spatula until just combined. Lastly, fold in the chocolate chips.
Pour the batter into the prepared pan and smooth out the top with a rubber spatula. Sprinkle more chocolate chips on top, as desired.
Bake the cookie cake for about 30-35 minutes until evenly golden on top and toothpick inserted comes out clean. Allow to cool completely in the pan.
For the chocolate frosting:
In a small saucepan, melt the butter over low-medium heat.
Once melted, turn the heat off, then add the chocolate, heavy cream, powdered sugar, cocoa powder, salt, and vanilla. Stir constantly until everything is melted and fully combined.
Pour the mixture through a fine mesh sieve into a medium bowl. Place in the fridge to cool, stirring every 10 minutes or so until it reaches a spreadable consistency. Leave at room temperature until ready to use.
Pipe the frosting onto the edges of the cookie cake, top with confetti sprinkles, and enjoy!
Notes
A note on browning butter... Start with a few extra tablespoons of unsalted butter, since water evaporates as it browns. Also, keep in mind that European-style butter has less water content, so if you're using American-style butter you might want to start with even more butter.
Completely cool the cookie cake. Be sure to let the cookie cake cool completely in the pan and before decorating or the frosting will melt!
If the frosting is chilled too long... microwave it in 10 second increments until it softens up, then use an electric mixer to beat on low speed until smooth.