Preheat your oven to 350 degrees, and line a large baking sheet with parchment paper. Set aside.
In a medium bowl, stir together the flour, cinnamon, baking powder, salt, and espresso powder. Set aside. In a large bowl, or the bowl of a stand mixer, beat together the oil, brown sugar, molasses, milk, vanilla extract, and eggs until just combined and fairly smooth. Slowly beat in the flour mixture until a dough forms. Then, stir in the chopped dark chocolate and pecans until well distributed. Make sure there are no pockets of flour or sugar lurking at the bottom of your bowl- stir it to make sure it's very well combined!
Divide the dough roughly into two halves, which will be formed into long logs on the baking sheet. The dough will be glossy and very sticky, so you need to wet your hands to help form it into two long logs that are about the length of the baking sheet (with a few inches on each end of space), about 3 inches wide, and about 1 inch tall.
Bake in your preheated oven for 30-35 minutes, or until the logs are puffed, golden, and look dry on the outside. Cool on the counter for 15 minutes, or until they are cool enough to handle for slicing. Meanwhile, reduce the oven temperature to 325 degrees.
Slice the logs at an angle, creating that classic biscotti shape. They should be about 1/2-3/4 inch thick. Place each cookie back onto a parchment lined baking sheet. You don't need to leave room between the cookies as they will not spread or puff during the second bake, and you should be able to fit all the cookies onto one sheet. Return the cookies to the oven for 12-15 minutes, or until they look golden and feel firm. They will harden as they cool, so don't over-bake them! Cool and enjoy!