The sauce thickened up wonderfully and it began to smell really really great.
I crushed up some dry tortillas and added that, with a little more water, to the pan, and put the lid on.
Then I went for a bath. Big mistake.
When I came back to the kitchen, everything was a haze of smoke. It smelled like a bonfire, and didn't look much better. Somehow, my chilli had actually set itself on fire. No joke. I panicked and threw a jug of cold water over it (first I turned off the heat, so don't be alarmed) and in about a second the water had gone from cold to steam. I have no idea how the pan got so hot.
The result: no chilli. The house was visibly smoky for four hours after that. And I smell like an arsonist. I was NOT HAPPY!