Preheat oven to 400 degrees F. Remove stems from mushroom caps.
Finely chop the mushroom stems.
In a large skillet over medium heat, melt 1 tablespoon of butter. Add shallot, garlic and mushroom stems and cook for about 3-5 minutes (or until soft). Transfer the mixture to a medium bowl. Stir in cream cheese, crab, parsley, lemon juice and salt. Blend well.
In the same skillet over medium heat, melt the remaining 2 tablespoons of butter. Remove skillet from the heat and add mushroom caps to the melted butter. Gently coat the mushroom caps in the melted butter.
Place caps, stem-side up, on a parchment-lined baking sheet. Spoon about 2 teaspoons of crab filling into mushroom caps, gently pressing filling into caps.
If prepping ahead, cover with plastic wrap and refrigerate for up to 8 hours.
Bake, uncovered, for about 10-15 minutes (or until mushrooms are tender).