Preheat oven to 350°F (175°C).

Whisk eggs in a medium bowl until blended.

Add Nutella: Mix in 1¼ cups Nutella (reserving 1 tablespoon for topping) and whisk until smooth.

Mix dry ingredients: Add flour and a pinch of salt. Stir just until combined. Optional: Add a dash of vanilla.

Prepare pan: Press batter into a greased or parchment-lined 5×8″ baking pan.

Add topping: Drop reserved Nutella in dollops on top and swirl with a toothpick for a marbled effect, if desired.

Bake for 25 minutes or until center is set.

Cool and serve: Let cool completely, then slice into 8 bars. Optional: Sprinkle with flake sea salt for extra flavor.