Preheat oven to 350 degrees F (175 degrees C). Grease a 9x13 inch pan.
In a large bowl, whisk together the flour, baking powder, baking soda and salt.
In a separate bowl, beat together the butter and sugar until light and fluffy.
Beat in the eggs one at a time, then stir in the vanilla.
Alternately add the dry ingredients and buttermilk to the batter, mixing just until incorporated.
Stir in the chocolate chips.
Pour batter into prepared pan.
Bake for 30 to 35 minutes in preheated oven or until a toothpick inserted into center of cake comes out clean. Allow to cool before cutting into squares.