We have learned to apply Domain-Driven Design (DDD) patterns on greenfield projects and are now exploring how to leverage AI to deepen our domain understanding. However, most of our work involves refactoring existing applications. Architectural patterns like Onion Architecture offer a viable solution, but first, we must untangle our Big Ball of Mud using DDD principles. Crucially, we need to implement robust tests to support our refactoring efforts, ensuring the solution remains maintainable and, if needed, can evolve towards a microservices architecture.