For the shrimp stock, remove the heads from the prawns, the shells including tail and legs. Devein the shelled prawns by running a knife lengthwise and cutting a shallow split. Remove the vein.  You can also rinse any grit under running water. Once all the prawns have been shelled, place a large saucepan with 3 tbsp olive oil on high heat.  Once oil is very hot, add and fry the shells as you mix until they change colour, approx. six minutes.  Using a potato masher, give them a crush in the pot. Deglaze with the white wine, add the water and fennel seeds.  Leave to simmer on low heat for 25-30 minutes.  Strain liquid once done and toss out the shells.

Cut off the dark green part of the leek, leaving the light green part. Slice one third the stalk lengthwise from the green side only. Run under cold water to wash away any dirt holding the green part down. Once washed, continue to cut into quarters and slice finely.

Peel and chop your shallot as fine as you can. Place the butter in a pot or saucepan that has a lid. Turn on heat to low, add the shallots and chopped leeks, cover and sweat gently until soft.  Add salt and pepper and the white wine. Bring to a simmer and cover with lid. This can take approx. 15 – 20 minutes, keep checking it and cook until all the liquid has evaporated with lid on.

Transfer the content into the bottom of a gratin or baking dish.  The best gratin dishes are wide and shallow for extra crust.

In a large saucepan (the same as you cooked the prawns heads, rinsed) , place butter, once melted, add flour mix well and cook into a roux for a couple minutes.  Add a little of the shrimp stock and mix well into a paste to remove any lumps. Add the remaining stock and bring to a simmer until thickened.  Keep simmering on low heat five minutes to cook out any flour starches.  Add the cream, season with salt and white pepper. Taste it and adjust accordingly.

For the gratin, in a large (preferably non-stick) frying pan on high heat, add olive oil.  Once very hot, add scallops and cook a few seconds to just brown each side.  Remove and set aside in a separate bowl.  Repeat this step with the shrimp (prawns), then the fish. You want a little colour on the outside but the seafood should be raw in the centre.

Transfer the cooked seafood to simmering shrimp sauce, mix well, bring back to a slight simmer on the edges and pour content over the leek confit in your baking dish.

Mix the grated cheese with the panko breadcrumbs and sprinkle over the top of the gratin. Bake in oven for 20-25 min at 430°F – 220°C.  If the top isn’t brown, place under the hot grill for 5 minutes or until golden-brown. The content should be slightly bubbling on the edges when ready.  Rest 10 minutes before serving.