Bring 4 liters (about 4 quarts) of water to a boil and add the crabs. Cook for 10 minutes. Remove crabs and place in cold water to stop cooking. Remove lungs and organs and discard. Carefully pick the crab meat from the body. Rinse the shells and set aside. Crack the claws and remove the meat. Gently combine lump meat and claw meat together. Separate the eggs.
In a small pan melt 1 tablespoon butter and add the flour. Cook the flour and stir in the milk. Bring to a boil. Remove from heat and stir in the egg yolks. Beat the egg whites until stiff and fold in 3 tablespoons of Parmesan cheese and the herbs. Season with salt and cayenne pepper. Fill the crab shells with crab meat and cover with the sauce. Top each portion with small pats of butter and sprinkle with the remaining Parmesan. Bake in a 200°C (approximately 400°F) preheated oven for about 15 minutes.