1. Fold crêpes in half, pale surfaces inside, and lay, overlapping, on a plate.
2. In a bowl, mix orange and lemon peel with orange and lemon juice.
3. In a 10- to 12-inch frying pan or chafing dish over high heat, melt sugar, shaking pan often, until it turns amber, about 2 minutes. Reduce heat to low and add juice mixture all at once; sugar hardens. Stir until sugar dissolves. Add butter and stir until melted.
4. With 2 large spoons and working quickly, lay 1 folded crêpe at a time in sauce, turn over, fold crêpe again to make a triangle, and push to a side of the pan. Repeat to moisten and fold each crêpe, overlapping as needed to fit in pan.
5. Pour liqueur and cognac over crêpes; when liqueurs are slightly warm, about 30 seconds, ignite (not beneath an exhaust fan or flammable items). Shake pan or spoon sauce over crêpes until flame dies. Let simmer 1 or 2 minutes, then spoon crêpes and sauce onto plates. Accompany with ice cream.