Preheat the oven to 425F / 220C / 200 fan and line baking tray with greaseproof paper.
Mix the olive oil, red wine vinegar, dijon, garlic, salt and pepper together in a small bowl to make the vinaigrette.
Remove the leaves from the cauliflower and cut into 1/2 inch thick slices (or 1 - 1.5 cm thick slices.) Make sure you keep the base on the cauliflower so the slices don’t fall apart. Place the cauliflower steaks on a greaseproof lined baking tray and brush both sides with dressing. Par bake for 25 minutes, turn over after 15 minutes.
Add a slice of red pepper, meat, olives, pepperoncini, basil and two cheese slices per cauliflower steak and place back in the oven for 10 minutes until the cheese melts. Option to finish under the broiler if you prefer. Top with arugula, a drizzle of olive oil and cracked black pepper.