Preheat oven to 350°F. Line an 8 x 4 inch baking loaf pan with parchment paper.
Add eggs to a large mixing bowl (you can use a hand mixer or a stand mixer). Using the wire whisk attachment, beat eggs on highest speed for about 6 minutes. Beat the eggs until the mixture becomes more than triple in volume, changes color to a very pale yellow, and becomes very thick. To check if your mixture is ready, lift up your beater and watch the egg mixture that drizzles down from your beater back into the bowl. It should sit on the surface of your mixture for several seconds and not immediately sink in. See photo in post for reference.
Add hazelnut spread to a separate large mixing bowl. Fold in 1/3 of the egg mixture. Gently fold in the egg mixture using a spatula until no egg streaks remain. Repeat with another 1/3 and then remaining 1/3.
Pour batter into prepared pan. Bake for about 18 minutes. The brownies should be puffy but not fully set. When you apply pressure on the surface it should bounce back a little but not completely. Let brownies cool for a few minutes before cutting. As the brownies cool, they will sink down. The brownies can be enjoyed right away however the flavor and texture is even better if you wait a few hours.
Notes
You can bake this in a 9 x 5 loaf pan but your brownies will be thinner and you will want to reduce baking time.
Recipe can be doubled and baked in an 8 x 8 square baking pan. Baking time should be close to the same as the original recipe.
I used Nutilight* hazelnut spread and milk chocolate. This recipe should work with other sugar free hazelnut spreads but be sure to choose a sweet one because there is no additional sweetener in this recipe.
These brownies are sweet but not supersweet. They have the sweetness level of semisweet chocolate chips. If you want them to be sweeter you can add sugar free chocolate chips to the batter or add a chocolate frosting on top. You can also add a few tablespoons of sugar substitute like erythritol.
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If you are on a keto diet, please remember to look at net carbs and not just total carbs. The net carbs count excludes fiber and sugar alcohols (carbs from erythritol).
The nutrition information provided are only estimates based on an online nutritional calculator. This is not a comprehensive list of all the nutrients in the recipe (i.e., does not include vitamins, cholesterol, etc). I am not a certified nutritionist. Please consult a nutritionist or doctor for accurate information and any dietary restrictions and concerns you may have.