Combine flours, sugar, eggs, milk, 6 tablespoons canola oil, vanilla, and salt in a large measuring cup or bowl. Stir well with a wire whisk until smooth. Let stand for 15 minutes.
Heat a 10-inch skillet over medium heat until hot. Brush with a generous bit of oil. Pour scant 1/4 cup batter into skillet and tilt pan quickly to coat bottom. Cook crepe until golden on bottom, about 30 seconds. Carefully flip crepe with a spatula and cook other side for an additional 30 seconds. Transfer to a plate, stacking crepes between wax paper, so they don’t stick together. Continue with remaining batter, brushing skillet with oil between crepes.
Spread a thin layer of nutella on one crepe. Place on serving plate. Spread a thin layer of nutella on another crepe; place on top of crepe on serving plate. Continue to spread nutella and stack remaining crepes. Spread a bit of nutella on top crepe. Top with chopped hazelnuts, if desired.