1 stick butter — unsalted
1 1/4 cup semisweet chocolate chips
1 cup all-purpose flour
1 1/2 teaspoons baking powder
1/4 teaspoon salt
1 cup light brown sugar
1 teaspoon vanilla extract
1 large egg
Heat oven to 350°F. Grease and line a 9″ cake pan.
Whisk the flour, baking powder and salt together. Cream the butter, light brown sugar and vanilla together until well combined, about 1 minute. Beat on high for another 15 seconds. Scrape down bowl and add the egg. Blend for another 30 seconds.
Add the dry ingredients and blend on low speed, then add the chocolate chips and blend until combined.
Scrape into the prepared pan. Flatten batter to an even layer, smoothing it out. Bake until light golden brown and puffy, about 18 to 22 mins (mine took 19).
Cool in the pan 10 mins, run a spatula around the edge to loosen. Cool completely (around 4 hours) and then turn out onto a serving platter.