Heat oven to 400°F Brush pan with vegetable shortening or butter. In a large bowl, sift together flour, sugar, baking powder, baking soda, and salt. Blend butter into the flour mixture with a pastry blender or two knives. The mixture should look like course meal. Stir in chocolate chips. In a small bowl, combine buttermilk and vanilla extract and then add to the flour mixture. Stir just until the dough comes together. Do not over mix the dough. Divide dough evenly among wells in pan. Bake for 13-18 minutes, until golden brown and toothpick comes out clean. Cool 10 minutes in pan. Remove from pan and serve.