In a small bowl, whisk together the flour, baking powder, soda and salt. In a large bowl, whisk together the eggs, sugar and vanilla extract until smooth. Whisk in the melted butter until combined. Stir in half of the dry ingredients. Pour in the buttermilk, then add the rest of the dry ingredients and stir until you have a smooth batter. Fold in the chocolate chips. Pour the batter into the greased pan and bake for 25 to 30 minutes, or until the cake is just set in the middle. Let cool for 20 minutes before gently turning the cake out on to a cutting board. Let cool completely before frosting.