Combine the flour, eggs, milk and 2 Tbsp. (30 mL) Grand Marnier in a blender or food processor.
Process into a smooth batter.
Refrigerate overnight.
Use a small (6" or 15 cm) crepe pan to prepare the crepes in your usual manner. (A non stick inner coating on the pan is a big help!)
Stack the crepes with paper towel between. (You should get about 8 crepes from this mixture.)
Heat the butter in a skillet (on the stove) or flambe pan (for cooking at the table) until it bubbles.
Add the sugar 1/2 c. (125 mL), Grand Marnier, juice from 3 oranges and the lemon.
Grate 1 of the oranges and add the rind to the pan.
Stir constantly and add the crepes, one at a time.
Turn each crepe carefully to fully soak it in the sauce and fold into 4.
Push each to the end of the pan before adding the next one.
Add the remaining 1/2 c. (125 mL) Grand Marnier.
Tip the pan and hold a lighted match to it — flame the sauce; stir it over the folded crepes until the flames disappear.