Preheat oven to 400 degrees Fahrenheit.
Place whole cauliflower in steamer basket or in pot of simmering bone broth. Cook until tender, 30-45 minutes.
Carefully remove using tongs and allow to cool slightly.
While cauliflower is cooking, sprinkle gelatin over water in small saucepan. Allow to dissolve for 1 minute. Then heat and stir for 2-3 minutes, until foamy and steaming, but not yet simmering.
Remove from heat and add cream, 1/2 the cheese, 1/2 tsp. sea salt and freshly ground pepper. (Add a few sprinkles of cayenne if you enjoy it.)
Chop stalks of mustard greens and begin to saute them over medium heat, using the 2 T. bacon grease or preferred fat. Add a pinch of sea salt. Cook for 8 minutes. While they saute, chop mustard green leaves into bite-size pieces and add them to pan after the 8 minutes. Increase heat to medium high and add 1/4 tsp. sea salt.
Continue to cook until greens are wilted, about 5 minutes more. Set aside to cool slightly.
Cut cauliflower into flowerettes and arrange them in a 2 quart casserole dish. (No need to grease it.) Using your fingers tuck in sauteed greens under and around flowerettes. Top with bacon pieces, tucking them into remaining crevices. Pour cream mixture evenly over all. Top with remaining 4 ounces grated cheese.
Bake for 30 minutes. Serve in shallow bowls, ladling the extra cream alongside the cauliflower; or serve on plates if preferred, reserving the cream for another use.