Preheat oven to 400°F (200°C). In a small skillet over medium heat, melt 2 tablespoons unsalted butter. Add the minced shallot and cook until translucent, about 2–3 minutes. Add the minced garlic and cook 30 seconds more until fragrant. Remove skillet from heat and let cool 2 minutes.

Combine filling

In a medium mixing bowl, add the lump crab meat and gently pick through to remove any shells. Add the cooled shallot-garlic-butter, lemon zest, lemon juice, mayonnaise, Dijon mustard, Worcestershire sauce, Old Bay seasoning, hot sauce (if using), chopped parsley, sliced green onions, salt, and black pepper. Fold ingredients together gently so you keep lumps of crab meat intact. Taste and adjust seasoning (add more lemon, salt or hot sauce as preferred).

Topping & assembly

Prepare topping

In a small bowl combine the panko breadcrumbs, grated Parmesan, and melted 1 tablespoon butter. Mix until crumbs are evenly moistened.

Fill baking dish

Lightly butter 4 small oven-safe gratin dishes or one 8x8-inch baking dish. Divide the crab filling evenly among the dishes, mounding slightly. If using a single dish, spread in an even layer.

Top and bake

Sprinkle the breadcrumb-Parmesan mixture evenly over each filled dish. Place dishes on a baking sheet to catch any drips. Bake in the preheated 400°F (200°C) oven until the topping is golden and the filling is hot, 12–15 minutes for individual dishes or 18–22 minutes for a single larger dish. If you want extra browning, finish with the oven broiler on high for 1–2 minutes—watch closely to avoid burning.

Garnish and serve

Remove from oven and let rest 2 minutes. Sprinkle with chopped chives or extra parsley and serve immediately with lemon wedges and toasted baguette or toast points.

Optional base (for serving)

If serving on baguette/toast points, preheat a skillet or toaster. Spread 1 tablespoon butter on both sides of baguette slices and toast in a skillet over medium heat or under the broiler until golden, about 1–2 minutes per side. Arrange under or beside baked crab and serve immediately.