In a medium mixing bowl, whisk together the eggs, flour, milk, melted butter and salt until smooth and well combined. Cover and refrigerate for at least one hour to allow the mixture to thicken.

Place 1 teaspoon of vegetable oil in an 8-inch nonstick pan and rub it over the bottom and sides with a paper towel. Heat the pan over medium heat and add about 3 tablespoons of the batter to the center of the pan. Quickly lift the pan from the heat, tilting and rotating until the batter coats it completely in a thin layer.

As soon as the crêpe appears set and "dry" (20 to 30 seconds), flip it over and cook until barely browned (10 seconds). Transfer to a plate and repeat with the remaining batter. If, after making the first crêpe, you feel the batter is a little too thin, whisk in a little additional flour (1 or 2 tablespoons at most). Stack the cooked crêpes on a plate as you work.

Fold 12 of the crêpes in half and set aside. (See the recipe notes about storing leftovers.)

Place the butter in a slightly larger nonstick skillet than you used for the crêpes and melt over medium-high heat. Add the sugar and orange zest and once it begins to bubble, add the orange juice and Grand Marnier. Continue cooking, stirring frequently, until the mixture thickens to the consistency of thin syrup, 4 to 6 minutes.

Place one folded crêpe in the syrup and quickly fold over again to form a triangle. Using a thin spatula, gently lift the crëpe from the pan, allow the excess sauce to drip off for a second or two, then transfer it to a serving platter. Repeat the process with the remaining crêpes, arranging them in a spiral around the platter. Drizzle the remaining sauce over the crêpes and serve immediately.