Preheat oven to 350ºF.

Wash mushrooms; remove stems, discarding any tough ends. Put mushroom stems in the bowl of a food processor and add crawfish tails, shallots, and garlic; pulse several times, scraping down the bowl as needed, until finely chopped.

Melt 3 tablespoons butter in a saucepan over medium heat. Add mushroom caps and sauté until softened, 5-8 minutes. Transfer stem-side down to paper towels to drain, then place stem-side up on a parchment-lined baking sheet.

Add crawfish mixture and bacon to hot pan; add Creole seasoning, lemon juice, thyme, lemon zest, and Maggi or soy sauce. Sauté until softened, 8-10 minutes. Remove from heat and stir in Parmesan and enough of the breadcrumbs to bring ingredients together. Taste and add salt, pepper, and cayenne as desired. Pack mixture tightly into mushroom caps, dot with butter, and bake for 15 minutes. Garnish with Parmesan and serve hot or at room temperature.