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["Adjust oven rack to lowest position and heat oven to 350 degrees.", "Cut 18"" length foil and fold lengthwise into 8"" width.", "Fit foil into length of 13 by 9"" metal baking pan, pushing it into corners and up sides of pan; allow excess to overhang pan edges.", "Cut 14"" length foil and fit into width of pan in the same manner, perpendicular to the first sheet.", "Spray with nonstick cooking spray.", "Whisk cocoa, expresso powder and boiling water together in large bowl until smooth.", "Add unsweetened chocolate and whisk until chocolate is melted.", "Whisk in melted butter and oil (may appear curdled).", "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 pieces.", "Scrape batter into prepared pan and bake until toothpick inserted halfway between edge and center comes out with just a few moist crumbs attached, 30-35 minutes.", "Transfer pan to wire rack and cool 1 1/2 hours BEFORE cutting.", "Using foil overhang, lift brownies from pan.", "Return brownies to wire rack and let cool completely, about 1 hour.", "Cut into 2"" squares and serve."]
