Make Biscuit Dough: In a large bowl, whisk flour, baking powder, baking soda, salt, and pepper. Cut in butter with a pastry cutter or fork until mixture looks like coarse crumbs. Pour in buttermilk and stir just until combined. Do not overmix. Refrigerate until ready to assemble.
Preheat oven to 450°F.
Make the Roux: In a 10-inch cast-iron skillet, melt butter over medium heat. Stir in flour and cook 5 to 6 minutes, whisking often, until the mixture is a peanut butter color.
Cook Vegetables: Add onion, bell pepper, and celery. Cook 3 to 5 minutes until softened. Stir in garlic and cook 1 minute.
Season and Simmer: Add tomato, Worcestershire sauce, thyme, bay leaves, and Cajun seasoning. Stir well. Slowly whisk in 2 cups stock and simmer for 5 to 7 minutes until slightly thickened. Add more stock as needed for a gravy-like consistency. Stir in cream and simmer 2 minutes. Season to taste with more Cajun spice, salt, and pepper.
Add Catfish: Gently fold in the catfish pieces. Remove pan from heat.
Assemble and Bake: Use a cookie scoop or spoon to drop dough balls evenly on top of the étouffée. Place skillet in the preheated oven and bake 30 to 40 minutes, until biscuits are golden brown and cooked through.
Serve: Garnish with green onions and parsley. Serve hot straight from the skillet.