In a tall container, such as a blender jug, place milk, flour, and a pinch of salt. Crack in the egg and add some water—about ⅓ cup (adjust the amount of water during mixing so that the batter is pourable and smooth). Mix thoroughly with a mixer or a kitchen whisk until the batter is uniform and lump-free.

Heat a non-stick pan very well. Warm and spread small amounts of butter or oil over the entire surface of the pan to fry 1 crepe. Pour a small amount of the batter into the center of the pan, then lift the pan off the heat and quickly swirl it to spread the batter evenly over the surface. Flip the crepe with a spatula after about 2 minutes (when the batter sets and light air bubbles appear underneath). Fry the other side of the crepe for a shorter time. Transfer the cooked crepe onto a plate. Prepare the remaining crepes in the same way until all the batter is used up.

Spread or smear the filling thinly over the crepes (divide the ingredients into as many portions as there are crepes). Fold the crepes in half and then in half again or roll them up into cylinders. Eat warm or cold.