Note About Seafood Seasoning
We found that the amount of sodium varied by brand. If using Old Bay, do not add any additional salt or do so to taste. For generic or low-sodium seafood seasonings, you may need up to ¼ teaspoon salt to season the filling. If you are not sure, in step 2 once you beat the cream cheese and seasoning, taste a small amount. If it tastes salty, do not add any additional salt (the crab is naturally salty too.)
The filling can be made up to 1 day ahead. The portobellos can be prepared up to 1 day ahead. Keep both separately in an air-tight container, stuff, top and bake just before serving.
These mushrooms can be reheated in the microwave for 90 seconds per mushroom. They do not freeze well as the mushroom becomes watery and has an unpleasant spongey texture.
Low Carb Option
You can use a keto breadcrumb product to make this a keto-friendly recipe, but do not add any additional salt and look for a low-sodium seafood seasoning.