Season the sole fillets and arrange them in a baking dish. Refrigerate until ready to use.
Shell the small prawns.
Remove the earthy stems from the mushrooms, rinse under cold water, and pat dry.
Shell the cooked prawns. Peel and slice the shallots. Snip the chives with scissors.
In a food processor, finely chop the cooked prawns, shallots, mushrooms, walnut kernels, chives, and olive oil. Season to taste and set aside.
Heat the olive oil in a cast-iron casserole over medium-high heat.
Add the sole trimmings and bones, onion, carrot, and slivered mushrooms. Season and sauté for 3 minutes.
Pour in the wine and stir, reducing for 2 minutes. Add the chicken broth and simmer gently for 30 minutes.
Strain the sauce through a fine sieve into a saucepan. Reduce over high heat until thickened.
Lower the heat and whisk in the butter gradually. Adjust seasoning.
Preheat the oven to 240°C with fan assistance.
Spread the prawn stuffing evenly over the sole fillets and bake for 6 minutes.
Meanwhile, sauté the peeled small prawns in butter over high heat for 1 minute. Season.
Arrange the sole fillets on plates, surround with sautéed prawns, drizzle with sauce, and garnish with chives.
Source: Ducasse's Kitchen by Sophie
