A couple days ago I made the fatal error of walking away from the stove while making a balsamic reduction in my Le Creuset saucepan. Smoke alarm went off, rolling boil of blackened mess stuck to the bottom of the pan that would not even flake off and was a good 1/2 inch thick of molten lava lol.
I tried cleaning it with a Mr Clean magic erase pad and then a plastic kitchen scraper. Finally I decided to google it. I've never abused a pan this badly. I found a post online from someone who said they did similar, and after contacting Le Creuset they were told to use 1 part laundry detergent and 2 parts water and boil it in the pan, repeating as necessary.
I did it once and after it cooled took the plastic scraper to it which got the lava off, but left a solid black coating on the pot, with a couple of scratches that showed the clean enamel underneath. A broke out the bar keepers friend and a plastic scrubby sponge and went to work. I got every speck of black off, it didn't even effect the sheen of the enamel and it looks new.
I was afraid I'd ruined it, but it all worked out.