Add the vanilla ice cream, Nutella, cold milk, ripe banana, and vanilla extract into a blender.
Blend at high speed until achieving a creamy and smooth consistency, ensuring thorough combination of all ingredients.
Taste the milkshake and modify sweetness or thickness by incorporating more Nutella or milk as necessary. Re-blend after any adjustments.
Halt the blender when content with both taste and texture. Check for any remaining Nutella or banana pieces; if needed, blend for a few additional seconds.
Take two serving glasses and drizzle extra Nutella within, allowing it to elegantly cascade down the glass sides.
Gently pour the prepared Nutella milkshake into the glasses, filling them around 3/4 of the way.
Optionally, crown the milkshake with a dollop of whipped cream and a scattering of chopped hazelnuts for heightened flavour and texture.
Serve the Nutella milkshake immediately and relish the experience!