Ouch, Jeff. I would start by using white vinegar, enough to cover the bottom of the pan and let it sit awhile to help loosen up the burnt stuff. Then - drawing on my past experience in a fine-dining resto as a dishwasher - then REALLY scrubbing at it with those green scouring pads, try some baking soda too and lots of elbow grease. Go to Bulk Barn and get a lot of baking soda (it's very cheap) - make sure it isn't baking powder, which looks just like it but is 3x more $$$!! I would NOT use SOS pads due to the chemicals in them. That and the fact that they seem to rust out right after you use them! Then rinse is best you can with multiple changes of hot water til there is no odour of any kind left. Hope this works!!
Been tapping since 2008.
2018 - 17 taps/7 trees...819l sap, approx 28l syrup
2019 - 18 taps/8 trees...585l sap, 28l syrup...21:1 ratio
2020 - 18 taps/8 trees...890.04l sap...gave away about 170l, 30l snafu'd....23l total for me from approx 690l
2021 - 18 taps/8 trees...395l sap, 12 l syrup
2022 - 18 taps/8 trees....7 sugars 1 red due to #2 having surgery so had the season off....582l sap, 18.5l syrup
2023 - 18 taps/8 trees...all sugars again. 807l sap, so far approx 14l syrup