Preheat the oven to 375°F and line a rimmed baking sheet with parchment paper.
To prepare the “crab” mixture, place the hearts of palm, shallot, garlic, and parsley in a food processor and pulse just until the ingredients are finely chopped, 30 seconds to 1 minute. Do not overprocess the mixture.
Heat 1 tablespoon of the olive oil in a large nonstick skillet over medium-high heat. Once the oil is hot, add the hearts of palm mixture and season with the Old Bay. Cook, stirring often, for 6 to 8 minutes, until the mixture is heated through.
Transfer the filling to a large bowl and add the cream cheese, ¼ cup of the breadcrumbs, and the parmesan. Mix well to thoroughly combine the ingredients. In a separate large bowl, toss the mushroom caps with the remaining tablespoon of olive oil and the salt. In a third bowl, stir the remaining
½ cup of breadcrumbs with the melted butter, garlic powder, and red pepper flakes. Set aside.
Working with one mushroom cap at a time, carefully spoon 2 to 3 tablespoons of the filling into each cap, depending on how big it is. Place the stuffed mushrooms on the prepared baking sheet and top each one with a spoonful of the breadcrumb mixture. Bake uncovered for 25 to 30 minutes, until golden brown and crispy on top. Garnish with minced parsley and serve immediately with lemon wedges