Make the filling: Combine the pecans and vanilla sugar in a food processor. Pulse until the pecans are ground into a fine powder, then transfer to a bowl. This can be done 1 day ahead to let the vanilla infuse with the nuts.

Make the pancakes: Whisk together the flour, butter and egg yolks in a medium bowl until smooth, then slowly whisk in the milk to incorporate. Combine the egg whites in a separate bowl with the granulated and vanilla sugar. Using an electric mixer, beat until stiff peaks form, then carefully fold into the flour-and-egg mixture.

Heat a greased, 10-inch nonstick skillet over medium heat. Pour ⅔ cup of batter into the pan and swirl to coat the surface evenly. Cook until the pancake has risen and is golden brown on the bottom, 2 to 3 minutes. Using a rubber spatula, carefully transfer the pancake to a platter, cooked-side down. Sprinkle the top, which will still be slightly uncooked, with ⅓ cup of the pecan filling.

Repeat the process 5 more times, stacking each pancake on top of the last. For the 6th pancake, flip onto the stack cooked-side up.

Let sit for 5 to 10 minutes until the pancakes firm up, then dust with confectioners’ sugar, slice and serve.