For the brownies
1/3 cup Dutch-processed cocoa
1 1/2 teaspoons instant espresso (optional)
1/2 cup plus 2 tablespoons boiling water
2 ounces unsweetened chocolate, finely chopped
4 tablespoons (1/2 stick) unsalted butter, melted
1/2 cup plus 2 tablespoons vegetable oil
2 large eggs
2 large egg yolks
2 teaspoons vanilla extract
2 1/2 cups sugar
1 3/4 cups unbleached all-purpose flour
3/4 teaspoon table salt
6 ounces bittersweet chocolate, cut into 1/2-inch pieces
For the topping
1/2 cup packed brown sugar
1/2 cup corn syrup
1 tablespoon vanilla extract
1/4 cup butter, melted
4 tablespoons bourbon/whiskey
2 cups chopped pecans
Heat oven to 350F. Make a foil sling for your 13 x 9 inch pan. Spray with nonstick cooking spray.
Whisk cocoa, espresso powder (if using), and boiling water together in large bowl until smooth. Add unsweetened chocolate and whisk until chocolate is melted. Whisk in melted butter and oil. Add eggs, yolks, and vanilla and continue to whisk until smooth and homogeneous. Whisk in sugar until fully incorporated. Add flour and salt and mix with rubber spatula until combined. Fold in bittersweet chocolate pieces.
Scrape batter into prepared pan and bake 20 minutes (note: you will be baking it further with the pecan topping, so it is not done yet. Transfer pan to wire rack and cool 15 minutes.
Meanwhile, make the topping. Using an electric mixer, mix corn syrup and sugar until smooth. Add in eggs and vanilla and beat until combined, then add butter and whiskey. Once mixture is thoroughly combined, fold in chopped pecans, then pour over brownies. Bake for an additional 30-35 minutes, or until pecan filling is set.
Using foil overhang, lift brownies from pan. Return brownies to wire rack and let cool completely, about 1 hour more. Cut into 2-inch squares and serve.