Someone gave me an individually wrapped frozen French Onion soup in plastic from Costco.
It came without instructions, but the Internet seemed to conclude that 40 mins at 400C was the answer.
I used the opportunity to use a clay French Onion soup bowl that's been in the cupboard for years. Probably bought at a yard sale.
The trickiest part was getting the frozen caramel cylinder out of the shrinkwrap and fully contained within the clay bowl, which wasn't very deep.
I happened to have a rustic molasses loaf lying around, so I cubed a slice to toss in after. Was debating whether to toast it first to simulate stale bread/croutons, but ended up just cubing it fresh because it's already pretty dense.
Overall, everything turned out alright. The soup was gooey and yummy. The improvised croutons sucked up the bottom of a broth that was a little thin.
Not as good as the pub, but good for a lazy version.
One note was that the frozen cylinder was topped with white round cheese nubs. I assume this was mozzarella or similar because I doubt Costco is laying out for Gruyere.
The freaky thing was that some of the round bits maintained their shape in the caramelized broth even after 40 mins. The cheese seemed to be warm/cooked, but I don't think I've ever had French Onion with white cheese pebbles.