Start by preparing the sauce; combine the milk, studded onion, black peppercorns, cloves and bay leaf in a large saucepan. Bring to the boil, then remove from the heat and allow to infuse to one side. Strain the infused milk into a jug after 15 minutes.
Melt the butter in a large saucepan set over a medium heat. Whisk in the flour until you have a smooth roux and cook, whisking occasionally for 1 minute. Whisk the infused milk in a slow, steady stream into the roux until you have a thickened sauce.
Add the broccoli and simmer the sauce over a gentle heat for 6-8 minutes, stirring occasionally. Adjust the seasoning to taste then remove from the heat. Add the seafood to the sauce and stir well.
Preheat the grill to hot.
Spoon the broccoli and seafood sauce into heart-shaped ramekins. Sprinkle the breadcrumbs on top and place under the grill for 1-2 minutes until golden brown. Remove from the grill and let them stand for a minute before garnishing with sprigs of dill. Serve immediately.