Coquilles St Jacques

For the piped potatoes

• 1lb (450g) baking potatoes, peeled and cut into chunks
• 2 tbsp butter
• large pinch of freshly grated nutmeg
• salt and freshly ground black pepper
• 3 large egg yolks

For the scallops

• 8 large sea scallops
• ¼ cup dry white wine
• one 3in (7.5cm) piece of celery
• small sprig of thyme
• 4 whole black peppercorns
• 1 bay leaf
• 8oz (225g) white mushrooms
• juice of ½ lemon
• 3 tbsp butter
• 1 tbsp all-purpose flour
• ¼ cup heavy cream or créme fraîche
• ½ cup shredded Gruyére

Special Equipment:
• 4 large scallop shells
• Pastry bag with ½ in (1cm) plain tip

Prepare ahead

The shells can be can refrigerated for up to 4 hours before baking.

1. Boil the potatoes in lightly salted water about 20 minutes, until tender. Drain and mash with the butter and nutmeg, and season with salt and pepper. Stir over low heat about 2 minutes. Remove from the heat and cool slightly. Beat in the egg yolks. Transfer to a pastry bag fitted with a ½ in (1cm) plain tip.

2. Preheat the oven to 425°F (220°C). Bring the scallops, 2/3 cup water, the wine, celery, thyme, peppercorns, bay leaf, and a large pinch of salt to a boil over low heat. Cover and simmer for 1-2 minutes, just until the scallops look opaque on the outside. Strain over a bowl and reserve the cooking liquid.

3. Simmer the mushrooms and lemon juice in a small covered saucepan over medium-low heat about 5 minutes, or until tender. Season with salt and pepper. Uncover and boil over high heat until the liquid is evaporated. Add to the scallops.

4. To make the sauce, melt 1 tbsp of the butter in a saucepan over low heat. Whisk in the flour and cook for 1 minute, whisking constantly. Whisk in the reserved liquid and whisk until simmering and thickened. Simmer, whisking often, until slightly reduced. Remove from the heat and stir in the cream and ¼ cup of the Gruyére. Cut each scallop into 2 or 3 pieces and stir into the sauce with the mushrooms. Season with salt and pepper.

5. Spoon the mixture into each shell or ramekin and sprinkle the remaining Gruyére on top. Pipe a generous border of potato around the edges of each shell. Dot with the remaining butter. Bake for about 15 minutes, or until golden. Serve hot.