Prepare Dry Ingredients
Sift together flour, baking powder, salt, cocoa powder, and espresso powder.
Prepare Wet Ingredients
Melt butter, oil, and ⅓ cup sugar over medium heat. Remove from heat.
Whisk eggs, egg yolk, vanilla, and ⅔ cup sugar until combined.
Gradually whisk warm butter mixture into egg mixture.
Combine and Bake
Stir in dry ingredients and chocolate chips until just combined.
Bake at 175 degrees C for 28-30 minutes.
Cool completely before slicing.
