Preheat your waffle iron to a medium-high setting and lightly coat with non-stick cooking spray or melted butter.

In a large bowl, sift together the all-purpose flour, baking powder, sugar, and salt to ensure a light texture.

In a separate mixing bowl, whisk the eggs thoroughly before adding the milk, melted butter, and vanilla extract.

Make a well in the center of the dry ingredients and pour in the liquid mixture, stirring with a spatula until just combined; small lumps are acceptable.

Drizzle the warmed Nutella over the surface of the batter and use a butter knife to gently swirl it 3 to 4 times to create thick ribbons of chocolate.

Pour approximately 2/3 cup of the marbled batter onto the center of the hot waffle iron.

Close the lid and cook for 4 to 5 minutes, or until the steam stops escaping and the exterior is golden brown and crisp.

Carefully remove the waffle and repeat the process with the remaining batter, serving immediately to maintain crispness.