**Prepare the Bread:**
Remove the crusts from the bread slices and flatten each slice with a rolling pin.
**Add Nutella:**
Spread a generous layer of Nutella on one side of each slice of bread, leaving a small border around the edges. Roll each slice tightly into a cylinder.
**Mix the Egg Batter:**
In a shallow dish, whisk together the eggs, milk, and vanilla extract until well combined.
**Combine Cinnamon-Sugar:**
In a small bowl, mix the granulated sugar and cinnamon. Set aside.
**Cook the Rolls:**
Heat a skillet or frying pan over medium heat and melt the butter. Dip each roll into the egg mixture, ensuring it's fully coated, and place it seam-side down in the pan. Cook for 2-3 minutes, turning occasionally, until all sides are golden brown.
**Coat in Cinnamon-Sugar:**
Immediately roll the cooked Nutella rolls in the cinnamon-sugar mixture while they are still warm.
**Serve:**
Serve warm with optional toppings like whipped cream, fresh berries, or a drizzle of chocolate syrup.