Lay the salmon fillet portions, skin-side down, in a shallow flameproof dish, to fit snugly in a single layer. In a small bowl, mix together the mustard, ginger, garlic, honey and soy sauce or tamari, then spoon evenly over the fillets. Season to taste with salt and pepper.
Heat the grill on the hottest setting. Cook the salmon fillets under the grill for 10–15 minutes, until lightly charred on top and cooked through.
Meanwhile, to prepare the lime courgettes, heat the oil in a large nonstick frying pan, add the courgettes and cook, stirring frequently, for 5–6 minutes or until lightly browned and tender. Stir in the lime rind and juice and mint and season to taste with salt and pepper.
Serve the salmon hot with the courgettes.