Preheat oven to 350 degrees F. Spread the nuts onto a baking sheet and place in preheated oven 5-7 minutes until fragrant. Shake the baking sheet halfway through baking so the nuts will toast evenly. Remove nuts from oven and set aside to cool completely. Once cool, chop nuts and set aside.
In a large heavy bottomed saucepan, melt butter, unsweetened chocolate, and 1 1/2 cups chocolate morsels over low heat, stirring constantly; set aside.
In a medium bowl, combine flour, baking powder, salt and espresso powder; set aside.
In the bowl of a stand mixer fitted with the paddle attachment, beat eggs, sugar, and vanilla at medium speed until combined. Add flour mixture, beating well. Add chocolate mixture and beat until combined. Stir in remaining 1 1/2 cups chocolate morsels and pecans.
Drop dough by 2 tablespoonfuls, spacing about 2 inches apart on to parchment paper lined baking sheets. Bake the cookies, one sheet at a time, until edges are firm and centers appear cracked, 9-10 minutes, rotating the baking sheet halfway through baking. Cool the cookies on the baking sheets about 3 minutes; using a wide metal spatula, transfer the cookies to a wire rack and cool to room temperature.