PREPARE OVEN AND PAN: Preheat the oven to 350°F. Coat an 8x8 inch baking pan with cooking spray until the bottom and sides look shiny, about 30 seconds of spraying. Set the pan aside.
MIX NUTELLA AND EGGS: Crack 2 large eggs into a medium bowl and break up the yolks with a wooden spoon or silicone spatula. Add 1 1/4 cups Nutella chocolate hazelnut spread and stir slowly until the mixture looks smooth and glossy with no streaks of egg, about 1 minute. The batter turns a rich, even chocolate brown when it is ready.
ADD FLOUR AND SALT: Add the 1/2 heaping cup all-purpose flour and 1 teaspoon kosher salt to the bowl. Stir slowly just until no streaks of flour remain, about 30 seconds. A few small lumps are fine. Stopping here keeps the brownies soft and fudgy, and the gentle stirring gives you tender brownies every time.
FILL THE PAN: Pour the thick batter into the prepared pan. Use the spatula to spread it into the corners until the top looks level and the batter sits in an even layer.
BAKE: Bake for 20 minutes, until the top looks set with a thin, papery crust and the kitchen fills with the aroma of chocolate and toasted hazelnut. A toothpick poked in the center comes out with a few moist crumbs clinging to it. Moist crumbs mean fudgy brownies once they cool.
COOL AND CUT: Let the brownies cool in the pan for 15 minutes, until the pan feels warm but comfortable to touch. Cut into 16 squares with a disposable plastic knife. The plastic blade glides through like butter and keeps every edge clean, even while the brownies are warm.
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Notes
STORAGE: Store the brownies in an airtight container at room temperature or in the fridge for up to 1 week. They stay at peak fudgy texture for the first 3 to 4 days.FREEZING: Wrap each brownie individually in plastic wrap, then tuck them into a freezer bag. They keep at peak quality for up to 3 months. Thaw overnight in the fridge.INGREDIENT TIP: Room temperature eggs blend into the Nutella smoothly and give you an even batter. Set them on the counter about an hour before baking. For gluten-free brownies, swap in your favorite gluten-free all-purpose flour, same amount. The 1 teaspoon kosher salt balances the sweetness, and you can leave it out if you prefer a sweeter brownie.