Coat the maitake clusters with soy sauce, water, brown sugar, bay leaf, and olive oil. Let marinate 20–30 minutes.
Place mushrooms in a steamer. Steam for 8 minutes.
Lightly brush with olive oil and grill on the barbecue until edges are lightly charred.
Transfer grilled mushrooms to a bowl and add red wine, garlic, thyme, bay leaf, and black pepper. Marinate 1–2 hours (or overnight).
Place the marinated mushrooms in the oven. Roast for 8 minutes at 220°C / 430°F.
In a heavy Dutch oven or cocotte, add olive oil. Place carrots, baby onions, and cabbage. Add the roasted maitake mushrooms. Pour in the wine marinade.
Mix flour, water, and salt to form a stiff dough. Roll into a rope and place around the rim of the pot. Close the lid tightly to seal the pot.
Place sealed casserole in the oven. Cook for 45 minutes at 180°C / 355°F.
Break the dough seal and serve the bourguignon with mashed potatoes.
