Whisk flours, baking powder and salt in a bowl and set aside.
In a large bowl, whisk the sugar, egg, milk, oil, vanilla extract and mashed banana until combined.
Mix the flour ingredients into the wet ingredients, stirring or whisking until just combined.
Using a ¼ or ⅓ measuring cup, pour the batter onto a greased skillet or griddle set at medium-low heat. Cook on one side until bubbles evenly form, then flip and cook on the other side until golden brown.
To serve, spread Nutella on the pancakes or drizzle it over the top (or do both!). Garnish with sliced bananas and chopped hazelnuts.