Heat a large skillet over low heat. Starting with low heat is very important. Once pan is warm add in about a tablespoon of oil and lion’s main to the pan
Cook lion’s mane about 10 minutes, stirring occasionally until tender and cook through.
Sprinkle over 1/2 tsp of Old Bay or a similar Seafood Seasoning and cook mushrooms 1 minute longer. Transfer lion's mane to a large mixing bowl and let cool.
Meanwhile, using the same pan increase heat to medium and add in a little more oil and onions to the pan.
Sprinkle lightly with salt. Cook onions for about 5 minutes, stirring occasionally until translucent.
Turn off heat and add onions to bowl with lions mane and let cool slightly for about 5-10minutes
Combine remaining seafood seasoning, breadcrumbs, mayo, and parsley, a pinch of salt and pepper with the lions main and onions. Stir gently to combine
Taste mixture and adjust seasoning if needed.
Add in flax egg and stir gently to combine.
Cover mixture and chill in refrigerator for at least 1 hour.
Using 1/4 measures cup portion mixture into 6-7crab cakes and place on lined baking sheet. Don’t flatten the cakes too much, but use your hands to help gently shape them. They hold shape better and don’t over brown if you don’t over flatten them.