Begin by preheating your oven to 180°C/Fan 160°C/Gas 4. Line a generously sized roasting tin with a sheet of foil that has been lightly buttered.
Place the salmon in the centre of the foil, generously seasoning it with salt and freshly ground black pepper. Toss the sliced fresh root ginger and lemon slices around the salmon, then fold the foil over, sealing it securely to form a packet. Transfer this packet to the preheated oven and bake for approximately 25–30 minutes, or until the salmon is just cooked and displays an opaque appearance. Ensure that the foil packet remains tightly sealed. After baking, remove it from the oven and allow it to cool.
Next, thinly slice the mangetout, blanching them in boiling, salted water for 2 minutes. Drain and promptly cool them in cold water. Create crescent-shaped slices from the cucumber halves. In a spacious bowl, combine the mangetout, cucumber, and other vegetables, along with half of the chopped coriander.
Prepare the hoisin dressing by mixing the specified ingredients in a jug. Pour this dressing over the vegetables, ensuring an even coating.
Combine the listed ingredients in a small bowl, incorporating the remaining coriander.
Transfer the salmon to a serving platter, removing the ginger and lemon slices. Arrange a tidy line of vegetables down the centre of the salmon. The remaining vegetables can be presented in a separate bowl alongside the sweet chilli sauce.