I’ve had good luck with simple green and patience while it sits there.
You can also usually zap a wet sponge in the microwave long enough to get it steaming, then place it on top. Just be aware you’ll want to use tongs to move it.
That’s the real key with baked on stuff; patience. You have to let whatever you’re using have enough time to loosen the gunk up.
If those fail, oven cleaner works, but it’s pretty damn brutal. Make sure you have plenty of ventilation and follow all safety instructions for the cleaner.
A decent oven should have chrome that’s on there solid, so you can usually sand down carefully without issue. If the block is hard, and you watch what you’re doing, you won’t come in contact with the chrome until you’re at the thinnest level of the baked on stuff. That’s usually gong to be easy enough to remove with something like bon ami or barkeeper’s friend. It’s faster than the long soaks, but you do have the possibility of scratches (no matter how low) if you go too fast.