Place 1 tsp of the garlic into the butter, along with a good pinch parsley.
Gently fry the onion and remaining garlic in a heavy based pan until softened. Mix in the crab meat and just warm it through. Add the fennel and remaining parsley and spoon the mixture back into the shells.
Mix the breadcrumbs with the melted butter and parsley and pack tightly over the top of the crab mixture. Top each shell with 1-2 spoonfuls of the Hollandaise sauce. Place under a hot grill and grill until golden then serve immediately.