Step 1: Prepare the Hispi Cabbage. Remove any tough outer leaves. Cut the cabbage in half lengthwise through the core. If very large, cut into quarters, ensuring a piece of core remains attached to each section.
Step 2: Make the Miso Butter. In a small bowl, combine the softened unsalted butter, miso paste, minced garlic, soy sauce, and black pepper. Mix thoroughly until smooth and well combined.
Step 3: Heat Your Pan. Place a large, heavy-bottomed skillet (cast iron is ideal) or griddle pan over medium-high heat. Add olive oil and let it get shimmering hot.
Step 4: Char the Cabbage. Place the cabbage halves/quarters cut-side down in the hot pan. Cook undisturbed for 4-6 minutes, or until deeply golden brown and charred. Do not overcrowd the pan; cook in batches if necessary.
Step 5: Cook Through and Glaze. Flip the cabbage pieces over to their rounded side. Immediately brush a generous amount of the prepared miso butter over the charred cut surfaces. Reduce heat to medium-low, cover the pan, and cook for another 5-8 minutes, or until the cabbage is tender-crisp.
Step 6: Serve Immediately. Remove the cabbage from the pan and arrange on a serving platter. Drizzle any remaining melted miso butter from the pan over the top. Garnish with sesame seeds, spring onions, or chili flakes if desired. Serve hot.