Baked Wild Sablefish with Braised Shiitake Mushrooms

4 Tbsp (60 mL) each of mirin and dark soy sauce
2 Tbsp (30 mL) sake
1⁄2 Tbsp (7.5 mL) sugar
1 tsp (5 mL) finely grated ginger
4 – five ounce (4 x 150 g) wild sablefish fillets
mitsuba (Japanese parsley), finely chopped preserved yuzu skin, finely chopped
4 large fresh shiitake mushrooms (at least 4-inches/10 cm in diameter), stems removed
12 Tbsp (180 mL) dashi
3 Tbsp (45 mL) each of mirin and dark soy sauce
2 tsp (10 mL) sugar
1 tsp (5 ml) cornstarch mixed with 2 Tbsp (30 mL) cold water

In small saucepan mix together mirin, soy sauce, sake, sugar and ginger. Bring to a simmer over low heat until sugar dissolves. Remove and set aside to cool. Place fillets in a container just large enough to hold the fish and pour the marinade over. Cover with plastic wrap and refrigerate for 48 hours, turning halfway through marinating.
Make shallow, narrow criss-cross incisions on the top of each mushroom being careful not to cut through.
Combine dashi, mirin, soy sauce and sugar in a saucepan and heat over high heat until boiling. Add mushrooms, reduce heat to medium and cook turning often, for 10 minutes or until softened. Remove mushrooms from liquid and keep warm. Increase heat to braising liquid and reduce by half. Slowly whisk in enough cornstarch mixture to thicken slightly. Set aside warm.
Place marinated fillets onto a non-stick baking sheet and place into preheated 500°F/260°C oven for 10 to 12 minutes or until lightly golden.
Place mushrooms upside down in centre of warm serving plate.
Place baked fillet on top, garnish with chopped mitsuba and yuzu skin