Step 1

1. Preheat the oven to 170°C (325°F/Gas 3).

Step 2

2. Season the chicken with sea salt and freshly ground black pepper. Heat half the butter in a flameproof casserole dish over medium–high heat until foaming. Add the chicken in batches and cook for 2 minutes on each side, or until seared and golden, removing each batch to a plate.

Step 3

3. Melt the remaining butter in the dish. Sauté the shallot and garlic for 1 minute, then add the mushrooms and cook for a further 3–4 minutes, or until the mushrooms have softened.

Step 4

4. Sprinkle the mushrooms with the flour and stir for 30 seconds, or until well blended. Slowly pour in the wine and stir until smooth. Cook, stirring, for 1–2 minutes, or until the liquid is thick. Pour in the cream and stir until just bubbling. Remove from the heat and add the chicken, tarragon and lemon rind. Set aside.

Step 5

5. For the topping, sift the flour and salt into a bowl. Rub in the butter with your fingertips until the mixture resembles breadcrumbs. Stir in the herbs, then make a well in the centre. Using a flat-bladed knife, stir in 125 ml (4 fl oz/½ cup) of the milk to form a dough. Turn out onto a lightly floured surface and knead gently. Roll out to form a 20 × 35 cm (8 × 14 inch) rectangle and brush with some of the remaining milk. Roll the dough up from the long ends to form a tight roll. Cut into 1 cm (½ inch) slices.

Step 6

6. Arrange the dough slices over the filling and brush generously with the remaining milk. Bake for 30–35 minutes, or until the filling is bubbling and the topping is golden and firm to the touch. Serve hot.