Blend the flour, eggs, milk, water, melted butter, sugar, and a pinch of salt until smooth. Rest the batter for 30 minutes.
Heat an 8-inch nonstick skillet over medium heat and brush lightly with butter. Add a small ladle of batter, swirl to coat, and cook until the edges lift, about 45 seconds.
Flip and cook the second side for 20 seconds. Repeat, stacking the crêpes on a plate.
Make the Orange Sauce:
Melt the butter in a large shallow skillet over medium heat. Stir in the sugar, orange juice, and zest.
Simmer until glossy and lightly thickened, about 3 minutes.
Fold and Serve:
Fold each crêpe into quarters and place in the sauce. Warm gently, turning once, until coated.
Add the orange liqueur if using and simmer for 30 seconds. Serve two crêpes per person with vanilla ice cream.
Notes
Resting the batter improves the crêpe texture.
Keep the sauce glossy and gently simmering.
The orange liqueur is optional for a family-friendly version.