Method:

1. Preheat oven to 230°C. Whisk oil, mustard, garlic, and thyme in a small bowl. Using your fingertips or a rubber spatula, mix in breadcrumbs, squeezing or pressing to saturate bread, until evenly coated; season with salt and pepper.

2. Open up fish and place, skin side down, in a large ovenproof pan or on a rimmed baking sheet; season with salt and pepper. Top with breadcrumb mixture, pressing to adhere. Roast until breadcrumbs are golden brown and fish is cooked through, 10–15 minutes.

3. Serve fish with lemon wedges.