Preheat oven to broil. Position oven rack 6 inches from broiler. Line a large rimmed baking sheet with foil.
Bring a large dutch oven with salted water to a boil. Add spinach; cook, stirring constantly, just until wilted, about 1 minute. Drain; press to remove excess moisture. Set aside.
In a medium skillet, melt 1 tablespoon of butter over medium heat. Add onion and celery; cook until browned, about 3 minutes. Add Slap Ya Mama HOT Cajun Seasoning; cook stirring frequently, until brown and crumbly, about 15 minutes.
Add garlic; cook for 2 minutes. Add wine, and scrape any brown bits from the bottom of the pan. Continue cooking until wine reduces, about 30 seconds. Add spinach and salt; cook until liquid is almost evaporated, about 15 minutes. Remove from heat; stir in bread crumbs and remaining 2 tablespoons butter.
Arrange oysters on a prepared pan top each oyster with about 1 tablespoon sausage mixture.