If you have vinegar, try soaking the items in a vinegar solution. 3% to 5% acidity is typical for most white vinegar solutions in the USA, you may find similar solutions available. The acid in the vinegar will soften the charred deposits after about 30 to 45 minutes. I would start by warming the vinegar to about 45 to 50 deg C or about 125 deg F..Boiling the vinegar doesn't seem to help, warm is fine. The higher temperature will accelerate the action of the vinegar on the deposits.
Once the soak is completed, scrub with a stiff brush. Then wash as normal. You may need to repeat this several times in extreme cases.
One product that is useful for cleaning stainless is BAR KEEPERS FRIEND. It is a very fine powder cleaner that is formulated for stainless products. an excellent item.
Use with the vinegar soak method and you should be able to restore your utensils and other stainless cookware to almost new condition.
Try toothpaste, paste, not gel.