Preheat oven to 325ºF. Whisk together eggs and extract. Set aside.

Combine flour, cocoa powder, baking powder, salt, sugar, espresso grounds, chocolate chips, and white chocolate. Add dry ingredients to eggs until dough just comes together. Dough should be slightly wet, but manageable with floured hands.

On a lightly floured board, roll the dough into two logs, approximately 12 inches long, gently patting so that they are just under an inch in height. Place them on parchment paper on a baking sheet. Bake about 20 minutes, until tops are cracked. Cool to room temperature.

Reduce oven to 300ºF. Slice biscotti at an angle, each cookie about 1⁄2 inch thick. Bake 5-8 minutes, flip over, and bake an additional 5-8 minutes. The thickness of cookies and length of baking will determine how hard the biscotti become.

For Double Chocolate Espresso Biscotti, add 2 1/4 tsp espresso grounds. Proceed as for above recipe.