Cloud provider barriers still stand. After a decade of cloud computing, customers struggle to overcome the challenge of crossing multi-provider clouds to benefit from fine-grained resource distribution, business independence from CSPs and cost savings. Although increasingly popular, most adopted IaaS intercloud solutions are generally limited to specific public cloud providers or present maintainability issues. Remaining hurdles include complexity of management and operations of such infrastructures, in presence of per-customer customizations and provider configurations. The Infrastructure as Code (IaC) paradigm is emerging as key enabler for IaaS multi-clouds, to develop and manage infrastructure configurations. However, due to complexity of the infrastructure life-cycle, to heterogeneity of composing resources and to user-customizations, this approach is far from being viable. In this paper, we explore an aspect-oriented approach to IaC deployment and management. We propose Mantus, a IaC-based multi-cloud builder composed of an aspect-oriented Domain-Specific Language called TML, or TOSCA Manipulation Language, and a corresponding aspect weaver to inject flexibly non-functional services in TOSCA infrastructure templates. We show the practical feasibility of our approach, with also good results in terms of performance and scalability.