You can prepare the crêpes in advance, and even freeze them "plain."

1. Candy the clementine zests, cut into thin julienne strips, by cooking them in a mixture of water and sugar; drain.
2. Pour two-thirds of the warm milk into a bowl; add the salt, sugar, eggs and flour. Whisk vigorously until smooth. Add as much of the remaining milk as needed to obtain the desired consistency. 
3. Mix in the warm melted butter, clementine zests and Grand Marnier.
4. Cook the crêpes in a non-stick skillet or crêpe pan, following the basic method.
5. Just before serving, melt a little unsalted butter in a large skillet; once it begins to foam, add 30 ml (1 oz.) Grand Marnier ;
6. Reheat each crêpe in this mixture; fold into quarters; sprinkle with sugar and transfer to a plate. Serve hot.