To begin, preheat your oven to 200°C (fan 180°C). Line a baking tray with parchment paper for even cooking and easy clean up. Move on to preparing the glaze.
In a small saucepan, combine birch syrup, soy sauce, vinegar, garlic, ginger and mustard seeds. Simmer over low heat for 5 minutes until slightly thickened. Set aside to cool briefly. Transition to seasoning the salmon.
Pat salmon fillets dry with paper towel. Rub each with salt, black pepper and a touch of canola oil. This step helps the glaze cling to the fish. Move to glazing.
Arrange the fillets skin side down on the prepared tray. Brush a generous layer of birch syrup glaze over the flesh. Reserve some glaze for basting later. Proceed to roasting.
Place the tray in the preheated oven. Roast for 12–15 minutes, depending on thickness, until salmon is nearly cooked through. Transition to basting.
Halfway through roasting, brush another layer of glaze over the fillets. This builds a rich, caramelised coating. Continue roasting until just done. Move to final glazing.
Once removed from the oven, brush the salmon with the remaining glaze while still hot. This seals in flavour and gives a glossy finish. Move to garnishing.
Place salmon fillets on warm plates. Garnish with fresh dill or chives and serve with lemon wedges. Suggested sides include roasted root vegetables or wild rice for an authentically northern meal.