Melt 1 tbsp of the butter in a large, oven-safe sauté pan (not nonstick) over medium heat. Add onion; cook 5 minutes until softened. Pour in 1/2 cup of the chicken broth and the dates. Bring to a simmer; cook 2 minutes. Remove mixture to a bowl. Stir in chestnuts, bread crumbs, 1/2 tsp of the salt and the pepper.