Mix the miso paste with all the other ingredients up to and including the honey. Coat the salmon with half of the glaze, cover and marinate in the fridge for approx. 2 hrs. Set aside the remainder of the glaze.
Spinach and mushrooms
Mix the spinach with the oil and salt, transfer to the grill tray. Mix the oil with the thyme, sage and salt, add the mushrooms and mix well.
Place the salmon on the grilling plank. Brush the cut surface of the garlic with oil. Place the grilling plank with the salmon on the grill rack, place the garlic (cut side down) and the grill tray containing the spinach and mushrooms alongside.
Charcoal/gas/electric grill: Cover and grill the salmon, garlic, spinach and mushrooms over/on a low heat (approx. 150 °C, for approx. 10 mins.