1 large egg room temperature preferred, 2 teaspoons vanilla extract
With mixer on low-speed, slowly mix in buttermilk until completely combined.
1 ¼ cup buttermilk
In a separate, medium-sized bowl, whisk together flour, baking soda, baking powder, and salt.
2 cups all-purpose flour, 1 ½ teaspoons baking powder, ¼ teaspoon baking soda, ¾ teaspoon salt
Add the dry ingredients to the wet ingredients and use a spatula to gently fold together until batter is approximately 75% of the way combined (do not use an electric mixer for this step or you will over-mix your batter and the cake will be dense and dry).
Add mini chocolate chips and stir until chips are distributed and batter is completely combined.
1 cup mini chocolate chips
Spread batter evenly into prepared baking pan. The batter will be thick, this is expected and necessary to keep the chocolate chips from sinking in the cake as it bakes.
Transfer to 350F (175C) preheated oven and bake for 25-30 minutes or a toothpick inserted in the center of the cake comes out clean or with moist crumbs.
Allow to cool completely in pan before covering with frosting.
For Frosting
Place butter in a large bowl and use an electric mixer to beat until creamy.
1 cup unsalted butter
Gradually add powdered sugar, stirring until combined.
3 ½ cups powdered sugar
Add vanilla extract, salt, and 1 Tablespoon of heavy cream and beat until thoroughly combined (be sure to scrape the sides and bottom of the bowl).
1 ½ teaspoons vanilla extract, ⅛ teaspoon table salt, 1-2 Tablespoons heavy cream
Check consistency and add additional heavy cream if frosting is too thick to easily spread.
If you would like to make this a chocolate frosting, add cocoa powder here and stir until combined (most likely you will need at least an additional tablespoon of cream).
½ cup cocoa powder
Spread over completely cooled cake. Sprinkle with remaining chocolate chips.
¼ cup mini chocolate chips, for topping
Cut cake and serve directly from the jelly roll pan. Enjoy!
Video
Notes
Storing
Cover jelly roll pan with plastic wrap and store at room temperature for up to 3 days.