Instructions

• Preheat oven to 350°F. Line a 9" x 13" pan with parchment paper, leaving about 2 inches of overhang on opposite sides, and spray the parchment and pan with cooking spray.
• Melt chocolate and butter: place 6 tablespoons unsalted butter and 6 ounces semisweet chocolate chips in a microwave-safe bowl. Microwave in 30-second intervals, stirring after each interval, until the mixture is smooth. Set aside to cool slightly.
• Whisk dry brownie ingredients: in a bowl, whisk together 3/4 cup all-purpose flour, 1/4 teaspoon baking powder, and 1/4 teaspoon salt. Set aside.
• Beat brownie wet ingredients: in the bowl of an electric mixer fitted with the whisk attachment (or with a hand mixer), combine 1 cup sugar, 2 large eggs, and 2 teaspoons vanilla extract. Beat on medium speed until pale and slightly thickened, about 3–4 minutes.
• Combine brownie batter: add the melted chocolate mixture and 1/4 cup unsweetened cocoa powder to the beaten sugar mixture and mix until combined. Add the flour mixture and beat, scraping down the bowl as needed, until just incorporated.
• Bake the brownie base: pour the batter into the prepared pan and smooth the top with a rubber spatula. Bake at 350°F for 15 minutes (the brownie should be partially baked but not fully set).
• Make the cheesecake layer: in a clean bowl, beat 16 ounces softened cream cheese until smooth. Add 2 large eggs, 1/4 cup sugar, 2 tablespoons all-purpose flour, 2 tablespoons milk, and 1 teaspoon vanilla extract. Mix on medium speed until the cheesecake batter is smooth, about 3–5 minutes.
• Add cheesecake layer and bake: pour the cheesecake mixture over the partially baked brownie layer and smooth the top. Return the pan to the oven and bake at 350°F for 15–20 minutes, until the cheesecake layer is set (the center may still have a slight jiggle but should not be liquid).
• Cool completely: remove the pan from the oven and let it cool to room temperature on a wire rack.
• Make the Rice Krispies topping: in a small saucepan over low heat, combine 1 cup semisweet chocolate chips, 1 cup peanut butter, and 1/2 cup Nutella. Cook, stirring occasionally, until the chocolate and peanut butter are completely melted and the mixture is smooth. Remove from heat and stir in 3 cups Rice Krispies until the cereal is fully coated.
• Finish the bars: spread the Rice Krispies mixture evenly over the cooled cheesecake layer and press gently to level.
• Chill to set: refrigerate the assembled pan for at least 2 hours (until the topping is firm).
• Cut and serve: use the parchment overhang to lift the slab from the pan. Cut into squares and serve.