Hey Sarah! Honestly, I''ve never really needed something other than hot water and dawn to clean my french oven! If it needs serious cleaning, I''ve seen some Le Creuset cleaner on amazon.com specifically for their enameled cast iron - you can probably pick it up at Williams Sonoma as well! However, I would just let it soak in a hot bath of dish soap and hot water and see if that works, if not, try the cleaner, and let me know how it works! I''ve been curious!
When you say French oven, are you talking about a dutch oven (le creuset enameled cast iron)? If so, I just use dish soap and water with a noscratch sponge. I''ve also tossed mine in the dish washer on occasion when it''s gotten really gross.