In a medium bowl whisk together flour and baking powder.Stir in chocolate chips.
In another medium bowl beat with electric mixer, beat sugar, peanut butter and vanilla until frothy, about 2 minutes. Make a well in center of dry ingredients and pour in egg mixture. Stir just until moistened and dough forms. Shape the dough into a 13- by 3- inch log on baking sheets lined with parchment paper.
Bake log 30 minutes and set aside for 10 minutes. Reduce oven to 300 degrees.
Cut warm log crosswise on a slight diagonal into 1/2 inch thick slices, about an inch apart on baking sheet and return to oven for 12-15 minutes. Biscotti with be crisp when cooled.