Clean portobello mushrooms with a damp cloth, remove stems and scrape out gills lightly if desired. Pat dry. Using a small paring knife make a shallow X on the underside cap to help marinade penetration.

Make Koji soaking sauce

Whisk together koji seasoning/paste, soy sauce/tamari, rice vinegar, maple syrup, sesame oil, grated ginger and 60 ml water in a shallow dish. Taste and adjust: it should be savory, slightly sweet and tangy.

Soak mushrooms

Place each mushroom cap, gill-side up, into the sauce and let sit at room temperature for 20–30 minutes, turning once so both sides absorb the liquid. Reserve the remaining sauce for glazing.

Mix dredge and wet batter

In a shallow bowl whisk together the all-purpose flour, cornstarch, garlic powder, smoked paprika, 1 tsp kosher salt, and 1 tsp black pepper. In another bowl combine non-dairy milk and 1 tbs of the reserved koji sauce (if using a paste). This is your wet batter.

Prepare breadcrumb mix

Combine panko, fine breadcrumbs, dried oregano, ground mustard and 1/2 tsp salt in a wide shallow bowl. Break up any large panko pieces so the crust is even.

Dredge mushrooms

Remove mushrooms from the soak and let excess drip off for 1 minute. Dredge each cap first in the flour/cornstarch mix (shake off excess), then dip into the non-dairy milk batter, then press into the panko mixture to coat completely. Set aside on a rack while you heat the oil.

Fry mushrooms

Pour oil into a wide skillet or straight-sided pot to a depth of about 1.5–2 cm (roughly 1/2–3/4 inch). Heat to 175°C (350°F) — or until a small piece of bread sizzles and browns in ~45 seconds. Fry mushrooms in batches, cap-side down first, about 3–4 minutes per side until deeply golden and crisp. Maintain oil temperature between 165–180°C. Transfer to a wire rack set over a baking sheet and keep warm in a 90–100°C oven if needed.

Glaze mushrooms

Warm the reserved Koji sauce in a small saucepan over low heat for 1–2 minutes, stirring. Brush a thin layer onto each fried mushroom (both sides) to impart additional umami. Do not soak — just a light glaze.

WW slaw & toppings

Make slaw

In a large bowl combine shredded green and purple cabbage, shredded carrot and sliced green onion. In a small bowl whisk together vegan mayonnaise, apple cider vinegar, 1/2 tsp maple syrup and a pinch of salt. Toss dressing with the shredded vegetables until evenly coated. Taste and adjust acidity or salt. Sprinkle sesame seeds if using.

Prep kimchi and extras

Drain any excess liquid from the Living Goodness kimchi. Warm gently in a small pan for 30–60 seconds if you prefer warm topping. Lightly toast buns: heat vegan butter or oil in a skillet over medium heat and toast cut side of buns until golden, about 30–60 seconds.

Assembly & service

Assemble burgers while mushrooms are hot. Spread a thin smear of extra koji sauce or vegan mayo on the bottom bun (optional). Place a glazed fried portobello cap on the bun, top with a generous scoop of WW slaw, then add about 3 tablespoons (roughly 45 ml) Living Goodness kimchi on top of the slaw (or to taste). Add cilantro or microgreens if using. Close with the top bun and serve immediately with lime wedges on the side.

Leftovers and notes: To reheat, place fried mushrooms on a wire rack in a 180°C (350°F) oven for 6–8 minutes to re-crisp. Slaw is best consumed same day.