Preheat your oven to 200°C (400°F).
In a large pot, bring salted water to a boil and add the cubed sweet potatoes. Cook for about 15 minutes or until tender. Drain and mash with a bit of olive oil, salt, and pepper. Set aside.
In a mixing bowl, combine honey, Dijon mustard, 2 tablespoons of olive oil, salt, and pepper to create the marinade.
Place the salmon fillets on a baking tray and brush generously with the honey mustard marinade.
Scatter the corn and sliced mushrooms around the salmon on the tray. Drizzle with the remaining olive oil and season with additional salt and pepper.
Bake in the preheated oven for about 15-20 minutes or until the salmon flakes easily with a fork and the vegetables are tender.
To serve, portion the mashed sweet potatoes onto plates, arrange the salmon and vegetables on top, and garnish with fresh dill. Add sliced green onions or lemon wedges if desired.
