Preheat oven to 425F. (I used convection and then switched to regular bake after the first 5 mins)
Grease a jumbo 6 cup muffin tin with shortening.
In a bowl, combine flour, baking powder, baking soda, salt and chocolate chips.
In a larger bowl, whisk the butter and sugar.
Add eggs one at a time.
Add vanilla.
Alternate adding the dry ingredients and the buttermilk just until combined.
Divide evenly into the muffin cups using a large ice cream scoop.
Top with more chips.
Bake at 425F for 5 minutes.
Then lower to 375F and bake 15-17 minutes.