Preheat your oven to 200°C (180°C fan-forced / 400°F).
In a small bowl, combine the softened butter and gochujang paste. Mix well until fully incorporated.
Place the cabbage wedges on a oven-safe pan. Brush the gochujang butter generously over each wedge, making sure to work it into the layers so the flavour penetrates throughout.
Roast for 25–30 minutes, or until the outer leaves are deeply charred and the core is tender when pierced with a knife. Depending on the density of your cabbage, this may take up to 35 minutes.
While the cabbage is roasting, melt 1 tablespoon of butter in a small frying pan over medium heat.
Add the panko breadcrumbs, garlic powder, white sesame seeds, and black sesame seeds. Toast, stirring constantly, for 3–4 minutes until the crumbs are golden and fragrant.
Watch carefully, they can burn quickly.
Immediately tip the toasted breadcrumbs into a separate bowl to stop them cooking further.
Arrange the roasted cabbage wedges on a serving plate. Generously scatter the breadcrumb mixture over the top.
If using, drizzle chilli oil over the finished dish. Serve immediately.