Mix the dry ingredients. Preheat oven to 350°F / 175°C. Line a rimmed baking sheet with parchment paper. In a medium bowl, whisk together 2 cups (120g) flour, 2 tsp baking powder, ½ tsp Kosher salt, and ¼ tsp ground cinnamon.
Combine wet and dry ingredients. In a separate large mixing bowl, whisk together 6 Tbsp (85g) butter, 2 eggs, 1 cup (200g) granulated sugar, and 1 tsp vanilla bean paste or extract. Add half of flour mixture, then fold gently to combine.
Fold in pecans. Add remaining half of flour and 1 cup (155g) chopped pecans, then fold until just combined and some streaks of flour remain. The dough will be very sticky.
Form into logs. Dampen hands slightly with water. Divide dough evenly in two, then form each half into a rectangular log, about 8x3-inch long and about ¾-inch tall, making sure to leave about 4inch of space between logs on baking sheet. Continue to wet hands as needed if dough begins to stick. Smooth sides and tops of logs.
First bake. Bake for 25 minutes, turning the baking sheet halfway through. Let cool 10-15 minutes, then transfer logs to a cutting board. Using a serrated knife, slice each log into 1-inch thick pieces.
Second bake. Return biscotti to baking sheet, lining them up on their sides. Bake for an additional 25 minutes, flipping them over halfway through cooking. Transfer to a wire rack to cool.
Melt chocolate. When cool, place 1½ cups (255g) chocolate chips in a microwave safe bowl. Melt in 15 second increments, stirring after each time, until melted and completely smooth.
Dip in chocolate. Dip cooled biscotti in melted chocolate, allowing excess chocolate to drip off. Immediately sprinkle with remaining chopped pecans. Allow chocolate to harden, about 1 hour. Store in an airtight container and eat within 1 week.