1

Put the potatoes in a pan, cover with cold water and bring to a boil. Simmer for 15 minutes, or until the potatoes are tender. Drain and return to the pan, the mash with 15g of the spread and 100ml of the skimmed milk and set aside. Preheat the oven to 200°C, fan 180°C, gas mark 5.

2

Meanwhile, mist a large nonstick pan with cooking spray and fry the leeks over a medium-high heat for 5-6 minutes, until soft. Remove from the pan and set aside.

3

Reduce the heat to medium. Melt the remaining spread in the pan, then add the flour and cook, stirring, for 1-2 minutes until the mixture starts to smell biscuity. Gradually whisk in the milk until smooth and combined. Increase the heat and bring the mixture to a simmer. Cook for 4-5 minutes, stirring every now and then, until the mixture has thickened enough to coat back of a spoon. Season to taste then whisk in 60g of the cheese and the tarragon. Fold the fish pie mix, prawns and leeks into the sauce, then spoon into a 20cm square baking dish.

4

Spread the mash over the filling, then scatter over the remaining cheese. Bake for 25 minutes or until golden and bubbling.

5

Meanwhile, steam the beans and broccoli in a steamer set over a pan of boiler for 5-7 minutes, until just tender.

6

Serve the fish pie with the veg on the side.