Assemble ingredients and tools. Melt the butter in a 10 - inch skillet.
Remove the stems from the mushrooms, and set aside.
Place the mushroom caps on a sheet pan, brush with melted butter.
Turn the mushroom caps face-down and place under the broiler for a minute or more to precook them. They should just start to “give-up their water.”
Dice the reserved mushroom stems. Finely chop the fresh parsley and garlic clove.
In the remaining butter, cook the diced stems, garlic and clam liquid for five minutes.
Stir in the clams, white wine, fresh parsley, Old Bay seasoning and dried thyme. Cook briefly.
Spoon the mixture into the pre-cooked mushrooms caps and broil for 8 minutes, until mushroom caps are tender. Be sure to keep an eye on them!