Preheat the oven to 325°F (160°C), or 130°C for a fan oven, and line a baking sheet with parchment; set aside.
Whisk the flour, cocoa powder, baking soda, baking powder, and salt; set aside.
In a separate large bowl, cream the butter and granulated sugar together. Add the eggs and vanilla extract and mix well.
Add the flour mixture to the butter mixture and mix until just combined.
Fold in the mini chocolate chips.
Using a spoon, scoop the dough into two logs onto the prepared baking sheet (roughly 14” x 3”), making sure they are at least 4” apart for spreading. Using greased hands, smooth the tops and sides.
Bake in the preheated oven for 30-35 minutes until puffed up and cracked on top and a toothpick inserted into the center comes out clean. Allow to cool completely.
Slice the biscotti loaves on the bias about 1” thick, then return to the baking sheet, cut side up, and bake for 15-20 minutes, turning once halfway through. Allow to cool completely.
Notes
The dough will be soft. This is normal! Use your hands to shape the dough into log shapes. If you find it really difficult, you can chill the dough for 30 minutes or so and try again.
Try to make things even. It's best if your dough logs are about the same size and shape, and that the biscotti pieces are the same thickness. Do your best, but don't stress too much. The rustic shape of the biscotti is one of its defining features.
For slicing, a large, sharp chef's knife will be your best tool. A dull knife could squish the dough too much and leave you with flat cookies.
Try making them thinner. More delicate biscotti can be made if you slice the logs into thinner pieces. Bake them for only 5-10 minutes per side.
Mix-ins. Add up to a half cup of chopped nuts like almonds, pistachios, or walnuts to the dough. This recipe would also be delicious with some dried cranberries or white chocolate chips.
Add More Chocolate! Interested in making triple chocolate biscotti? Try melting some semi-sweet chocolate chips and drizzling the chocolate all over the finished, cooled biscotti. You can also dip one end into the chocolate and then into chopped nuts or sprinkles!