I did this a few years back with my grandmother's deadly vintage enamel pot so and the pool actually ate away the pot!

After trying the baking soda paste-no improvement, sorry to say. However, I did put a layer of Soft Scrub on it and left it for days and days. Did some good. However, the biggest fail was -scrubbing- it with Soft Scrub. It took off much of the shine of the enamel. After letting it sit for days with the Soft Scrub, I gently washed it off and with my fingernail was able to scratch off some burned bits. Will try the soapy bleach water soak next. Word up-as an earlier poster whom I'll call "Captain Obvious" stated, never, ever, ever make popcorn in your beloved Le Creuset.

Just ran across this link from the Le Creuset fan page on Facebook. Not sure that there's much new information, but maybe something will stick out. Good luck!

http://www.diylife.com/2011/01/11/cast-iron-pan-cleaning/

Also, I once read a suggestion for one part Tide to three parts water and let soak. Hey, if you're in a pickle, right?

I would recommend a several day soak with soapy bleach water. Don't scrub as you will dull the nice shiny finish on the enamel which will make it a less of a non stick surface and un-needed wear to the enamel which will shorten the life of your enamel. Bleach water has been the best soaking tip for baked on food that I have come across. Also, cascade complete has enzymes that work great for food removel and works well as a soaking solution.

You can also make a solution of water with LOTS of bakign soda, let the water boil away (watching carefully) and then peel out the baking soda; burnt bits come right out with it. Or at least they do on stainless steel. I'm not certain on enameled cast iron!

Enameled cast iron is a bad choice for popcorn. Okay, you know that already. I'd go with the water/vinegar solution, scraping vigerously with a wooden spoon.

Another suggestion would be to fill the pot with water and set it on the heat. Let it boil a bit, and then take a wooden spoon or paddle to try to loosen the crud. Sort of like deglazing with wine/stock brings up the fond....

But DON'T let the pan boil too long, or you'll have an entire other issue.

If you find you still have a dark residue on the enamel after you've gotten all the crud off, put a bleach solution (about 10% or so bleach in water) into the pan so the level is above the stain, and let it sit for a couple of days. It'll lighten it back up like magic,

If the baking soda doesn't work, vinegar is also great for removing stuck-on foods.

Tried soft scrub or an enzyme detergent like Biz ?

Am stuck at home for Snowmaggedon11, or the Snowpocalypse, take your pick. (in Atlanta, GA) No Barkeepers Friend in the house which I cannot leave. So, Lucytron, your suggestion of soaking with baking soda/then scrubbing with new sponge is on like donkeykong. Will report back in 24 hours, people. Thanks ever so much, Lucytron!

Soak with some baking soda and little bit of water for an hour or two, then use a stiff scrubber - like a new sponge or a brush. Baking soda and little time never fails me.

if regular dish soap doesn't work, then try a little bit of barkeepers friend. It's a gentle powder scrub. It's recommended by both Staub and LC and also All Clad