- 1 cup butter, softened
- 1 cup firmly packed brown sugar
- 2/3 cup white sugar
- 4 eggs
- 2 teaspoons vanilla extract
- 1/2 teaspoon salt
- 2 cups all-purpose flour
- 2 cups semi-sweet chocolate chips, divided
- Frosting:
- 1 1/2 cups confectioners' sugar
- 3/4 cup butter, softened
- 2 teaspoons vanilla extract
- Preheat oven to 350 degrees F (175 degrees C). Grease a 10 1/2×15 1/2-inch baking pan and line with waxed paper.
- Beat 1 cup butter, brown sugar, and white sugar together in a bowl using an electric mixer until smooth and creamy; add eggs, 1 at a time, beating well after each addition until smooth. Mix 2 teaspoons vanilla extract and salt into creamed butter mixture. Gradually stir flour into creamed butter until just incorporated; fold 1 cup chocolate chips into batter. Spread batter into the prepared pan.
- Bake in the preheated oven until lightly browned on the edges, 20 to 25 minutes. Remove from oven and cool completely.
- Melt remaining 1 cup chocolate chips in the top of a double boiler over simmering water, stirring frequently and scraping down the sides with a rubber spatula to avoid scorching. Beat confectioners' sugar and 3/4 cup butter together in a bowl using an electric mixer until smooth; add melted chocolate and 2 teaspoons vanilla extract and mix until frosting is smooth. Spread frosting over cooled cookie cake.