Preheat oven to 350F (175C) and spray a 10×15” (25x38cm) jelly roll pan with baking spray (or lightly grease and flour). Set aside.

In a large bowl, combine butter and sugar and use an electric mixer to beat until well-combined.

Add egg and vanilla extract and mix well.

With mixer on low-speed, slowly mix in buttermilk until completely combined.

In a separate, medium-sized bowl, whisk together flour, baking soda, baking powder, and 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.

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.

Place butter in a large bowl and use an electric mixer to beat until creamy.

Gradually add powdered sugar, stirring until combined.

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).

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).

Spread over completely cooled cake. Sprinkle with remaining chocolate chips.

Cut cake and serve directly from the jelly roll pan. Enjoy!