Combine the flour, milk, water, eggs, butter, and salt in a blender, and blend until the mixture is smooth—about 10 seconds. The batter should be much thinner than pancake batter—closer to the consistency of heavy cream.

Let the batter rest for at least an hour, and up to overnight.

When your batter is ready, heat your crêpe pan or nonstick skillet on medium, cut off a sliver of butter, and swirl it around your pan. Then use a paper towel to coat the pan evenly.

Pour about ¼ cup of batter directly in the center of the pan, then quickly lift the pan up and roll your wrist around as you hold it, so that the batter spreads out in a thin even layer over the pan.

Cook until you see the lacy edges begin to brown, then use a non-scratch spatula to flip your crêpe and cook the other side.

Keep an eye on your heat—you want the crêpes to cook for about 1 minute on the first side, and 30-60 seconds on the second side so they won't burn before they are cooked through.

Repeat with the rest of your crêpes, including buttering the pan between each.

As you finish your crêpes, stack them on a plate separated by squares of wax paper or parchment paper.

Spread each crêpe with a generous tablespoon of Nutella.

Roll up or fold over twice to make a triangular packet.