A Luxuriant Vegetable Pie

To start, prepare the vegetables; trim away a little of the stalk from the fennel, cut it in half through the root, then into 1cm slices.

Trim the leeks, keeping just a little of the dark green part, then slit them vertically to about halfway down and fan them out under the tap to remove any grit. Then cut diagonally into 1.5 cm slices. Trim away a small piece off the base of each broccoli stalk, then cut it into pieces about 6cm long.

Next, set a fan steamer over boiling water and first put in the fennel to one side, cover with the lid and set the timer for 1 minute then place the leeks next to the fennel and set the timer for 1 more minute followed by the broccoli next to the leeks for 2 minutes and finally, add the broad beans and steam for a further 2 minutes, by which time all the vegetables should be al dente and still retain their colour.

Then remove them from the steamer into a large bowl to cool.

Preheat the oven to 200°C/gas mark 6 with the baking tray.

To make the sauce, melt 40g of the butter in a medium saucepan then stir in the flour and gradually whisk in the stock.  Bring it up to a simmer, then cook very gently for 4–5 minutes. After that, remove from the heat and stir in the two-thirds of the cream and some seasoning.

While the sauce cools, roll a little over half the pastry to a 28cm round on a floured surface (giving it quarter-turns to form the round), then line the sandwich tin, pushing it well into the edges and leaving the overhang for the moment.

Now take the cooled sauce and whiz the watercress into it either with a stick blender or a processor until the sauce is green but still has some flecks of watercress in it. Put a quarter of the sauce into the bowl with the cooked vegetables and reserve the remaining sauce in a cool place for later.

Now add the toasted pine nuts, capers and cornichons to the vegetables and gently give it all a thorough mix to coat everything lightly, adding a little more sauce if necessary. Have a taste now and add more seasoning if necessary before piling it into the lined pastry. Now roll the remaining pastry 3mm thick and 24cm wide and dampen the edges of the base and lay the lid on the top.

Pinch the base and the lid well together where they overlap the tin, then use a pair of scissors to trim away the excess pastry, leaving a 1.5cm overhang. Fold in the overhang using your thumb and forefinger to form a scalloped edge. Roll and cut some leaves with the pastry trimmings and use them to decorate the top. Brush all over with the egg glaze and use a skewer to make a hole in the centre for the steam to escape. If you want to make this in advance refrigerate and leave the glaze until later.

Put the pie on the hot baking tray and bake for 40 minutes. When the pie comes out of the oven, leave it to stand for about 5 minutes.

Heat the sauce in a medium saucepan without boiling and, when it is hot, whisk in the last 15g of butter and 50ml cream before removing from the heat and pouring into a warmed jug. Carefully remove the pie from the tin, then serve whole or cut into wedges on warmed plates with the hot sauce and some extra watercress to garnish if you like.