Preheat oven to 325ºF.
In a large bowl add eggs, salt, and pepper; whisk well. Whisk in half & half. Slice bread into one-inch chunks and add to egg mixture; mix well. Allow to absorb at least 20 minutes.
Heat oil in a large skillet over medium-high heat.
Add onions; sauté five minutes. Add bell pepper, celery, garlic, and tasso; sauté five minutes. Remove from heat; add chopped crawfish with fat and green onions. Let cool at least 10 minutes. Add to bread mixture; stir just until combined.
Pour mixture into a greased 13x9-inch baking dish. Bake for 55 to 60 minutes until bread pudding has set. Transfer baking dish to a wire rack and let rest 10 minutes before serving; garnish with fresh basil if desired.