Makes 5-6 crêpes, but the recipe is easily multiplied
1 tbsp unsalted butter 1/3 cup + 1 tbsp all purpose flour Big pinch of fine sea salt 1 egg 1/2 cup milk 1-3 tsp water 1/4 cup hazelnuts 5-6 heaping tsp of Nutella
Melt the butter in a large, sturdy frying pan. Keep heating until the foam dies down and the butter is full of rusty flecks. Pour into a bowl to cool.
Tip the flour and salt into a mixing bowl and whisk together. Make a well in the middle then break the egg into it. Whisk in, incorporating some of the flour. Pour in a bit of the milk and whisk in, slowly incorporating all the flour and milk. Add one teaspoon of water, reserving the others to change the consistency if needed—it should be around double cream. Whisk in the brown butter. Scrape the batter into a jug, to make pouring easier (or use a ladle). Leave to sit for a few minutes.
Turn the heat back on and add the hazelnuts to the pan. Toast for a few minutes until the hazelnuts start to smell good and brown. Tip the nuts out onto a cutting board and chop into small pieces.
Place the pan over a high heat—once you can feel a strong heat when you hold your hand a few inches above the pan, turn the heat down a bit and add a small knob of butter and swirl around (if the pan is hot enough, the butter browns almost immediately after it melts). Holding the pan at an angle, pour a bit of the batter into the pan at the top and swirl into a thin layer. When it starts to brown around the edges, flip. Once that side is done, flip onto a plate and immediately spread with a heaping teaspoon of Nutella, sprinkle with some hazelnuts and fold up.
Adjust the consistency of the batter with a teaspoon or two of water if the pancake is too thick. Repeat, melting a little butter in the pan each time. The batter keeps in the fridge for a day (just whisk it back together before using).