For the onions: You can make these on a grill over open flame with a perforated pan. You can also make them in a saute pan. To make over a grill, toss the sliced onions in a bowl with oil, sugar, vinegar and some salt and pepper. Allow to marinate for about 20 minutes. Pour into a perforated pan and place directly on the grill over the flame. Stir constantly until all the onions are cooked and golden brown. To make in a saute pan, add the oil to a hot pan and then add the onion. Stir occasionally to allow the onions to caramelize, then deglaze with the cane vinegar. Remove from the heat and finish with the brown sugar and some salt and pepper. Let cool.
For the potatoes: Rinse and quarter the red potatoes. Season 8 cups water with the seafood boil spice and bring to a rapid boil. Add the potatoes and simmer for about 10 minutes. Remove from the water and let cool.
For the greens: In another shallow saute pan, add the butter and place over medium-high heat. When the butter is melted and sizzling, add the minced garlic. Let the garlic toast to a light golden brown, and then add the greens. Stir to coat the greens with the garlic. Add the cane vinegar. Season with salt and black pepper. Toss just to wilt the greens and remove from the heat.
For the fish: To clean the snapper, the first thing you want to do is scale and gut the fish. Then use a pair of scissors to remove the gills and all the fins from the outside of the fish. Cut an "X" on both sides of the snapper.
While the oil is heating, sprinkle both sides of the fish with the Creole seasoning and some salt and pepper. Then dredge in the seafood breading. Be careful not to bread too heavily. Bend the fish so it will look like it is swimming when it comes out the fryer. Cook the crab boiled potatoes in the oil with the fish until crisp and golden brown.
To serve, quickly heat the barbequed onions in the pan. Toss with the garlic wilted greens and crab boiled potatoes. Place the onions, greens and potatoes on the bottom of the plate and fish in the center of the plate and drizzle with the guava ketchup. Garnish with fresh herbs and serve hot.