Preheat oven to 350 degrees F. Cut cabbage into bite sized chunks and place into an oven and microwave safe covered casserole dish. Sprinkle all over with Greek seasoning, toss, sprinkle again. Cut butter into slices and scatter on top. Cover and microwave for 15 minutes; set aside and keep covered. Meanwhile, melt the remaining 2 tablespoons butter in a skillet and saute the celery and onion until tender. Sprinkle the flour over the vegetables and cook for about 3 minutes. Stir in the half and half and continue cooking for another 3 minutes until mixture is smooth adding additional half and half to make mixture thick, but pourable. Add in the cheese and Cajun seasoning and stir until cheese is melted and fully incorporated. Pour cheese mixture evenly over the cabbage. Add the Parmesan cheese to the bread crumbs and place evenly over the top of the casserole. Bake uncovered at 350 degrees F for 30 to 40 minutes, or until mixture is bubbly and topping is lightly browning.