Instructions

• Preheat oven to 325°F (163°C). Line an 8×8-inch square baking pan with parchment paper, leaving a 1–2 inch overhang on two opposite sides to use as handles.
• Open the jar of Nutella and spread it in a thin, even layer to fully coat the bottom of the parchment-lined pan. Place the pan in the freezer and freeze the Nutella layer for about 1 hour, or until it is frozen solid.
• When the Nutella is solid, remove the frozen Nutella (parchment and all) from the pan and return the empty pan to room temperature. Keep the frozen Nutella in the freezer while you make the batter.
• In a small saucepan over low heat, melt 4 tablespoons unsalted butter. Add the 8 ounces semi‑sweet chocolate and stir until the chocolate is completely melted and smooth. Remove the pan from the heat and whisk in ½ cup vegetable oil and 1 teaspoon vanilla extract. Set the chocolate mixture aside to cool until it is warm but not hot to the touch (a few minutes).
• In a large bowl, sift 1½ cups powdered sugar. Add 2 eggs plus 1 egg yolk and mix with a hand mixer or whisk just until combined; do not overmix.
• Pour the cooled chocolate mixture into the egg/sugar mixture and stir until combined.
• In a separate bowl, whisk together ¾ cup all‑purpose flour, 1 tablespoon cornstarch, and ½ teaspoon salt. Fold the flour mixture into the chocolate mixture with a spatula until just combined. Stir in ½ cup chocolate chips.
• Pour half of the brownie batter into the prepared 8×8 pan and spread it into an even layer.
• Remove the frozen Nutella slab from the freezer and place it, Nutella side down, onto the batter in the pan, centering it. If needed, press gently so it sits flat. Spread the remaining brownie batter evenly over the frozen Nutella (work quickly while the Nutella is still frozen).
• Bake in the preheated 325°F oven for about 35 minutes, or until the edges are pulling away from the pan and the center is set (a toothpick won’t be reliable because of the Nutella center).
• Let the brownies cool in the pan on a wire rack for 30 minutes. Using the parchment overhang, lift the brownies out of the pan and place them on the wire rack to cool an additional hour (they cut best when completely cool).