Thanks to everyone who participated in my recent poll about methods to clean a crusty pan. I have to admit I was relieved to know that other people resort to using a conventional synthetic sponge with both the yellow side and green scrubber side (51% of respondents). Of course this isn't a great environmentally sound solution, but these sponges do scrub really well.
Coincidentally, a few days after posting the poll I had a cooking disaster. The meal turned out fine, but the pan was one of the most baked-on disasters I have ever seen. In fact, the pan is still soaking in my kitchen, 5 days later. I've tried my natural brush (the pan laughed at it!) and then my synthetic brush. I also soaked it in hot water and then broke out the synthetic yellow/green scrubber sponge. Still not much progress.
I was loosing hope when a friend suggested I use baking soda and some boiling hot water. It helped! But there is still a little stubborn bit left. Might have to resort to using some steel wool (which 9% of poll respondents use) but I am concerned it might scratch my enameled porcelain pan. I might also try something called Bar Keepers Friend, which my friend told me about. It is an oxalic acid product, made from rhubarb. It is biodegradable, and contains no phosphates, bleach, or abrasive crystalline silica which may harm many surfaces. It looks like a pretty strong product, so I'm only exploring it as a last resort. Wish me luck! My only other option might be a chisel.