Martha's salmon en papillote with chipotle, sweet potatoes & onion

1. Stir together the chipotle paste, olive oil and lime zest and juice in a medium-sized bowl. Add the salmon. Cover the bowl and leave in the fridge for at least 1 hour, or better still overnight, to marinate.

2. Preheat the oven to 180°C, gas mark 4. Cut two large rectangles of baking parchment and lay each out on the work surface. Divide the sweet potato between each sheet of baking parchment. Top each pile with a fillet of marinated salmon, then scatter with the salad onions, coriander and season.

3. Fold the empty half of the parchment paper over the salmon and crimp the edges closed, as if making a square pasty. Repeat with the second piece of salmon, then put the parcels onto a baking tray.

4. Bake for 30-35 minutes, allowing an extra 10 minutes if the dish contains potatoes. The salmon should be tender and cooked through. Serve in the parcel, so none of the juices are lost, or transfer to plates and drizzle over the juices.