Place salmon fillets on parchment lined baking sheet. Prepare the marinade by mixing together the miso, vinegar, honey, soy sauce and sesame oil in a small bowl. Generously spread the marinade over each salmon fillet. Let marinate for 1 hour minimum or up to 3 hours in the refrigerator.
While the fish is marinating, prepare and cook the rice. Place dried shiitake mushrooms in 3 1/2 cups boiling water, turn off heat and let sit for 10-15 minutes. Use this water to cook rice. While dried mushrooms are steeping, sauté fresh mushrooms and garlic in olive oil over medium high heat for 5-8 minutes until soft. Set aside. Remove dried shiitake mushrooms from liquid and slice. Put rice in medium sauce pan and add shiitake water and sliced dried mushrooms. Cover, bring to a simmer, then lower heat and cook for 30-40 minutes or until rice is tender. Fluff rice with fork, add sautéed mushrooms, garlic and salt and pepper to taste. Drizzle a bit more olive oil if needed.
To cook the salmon, pre-heat the broiler and cook for about 5 minutes. Check for doneness and then continue to cook for about 3 more minutes, being careful not to overcook. You want to have a nice caramelization of the miso glaze. Serve immediately with shiitake mushroom rice and garnish with scallions. Serves 4-6.