Acceptance of blockchain-based distributed systems in industry requires a thorough justification of their depend- ability and security. To foster blockchain acceptance, this paper proposes a new engineering perspective rooted in classic tools and well-understood concepts used in industrial critical systems design. More in detail, the proposed approach transposes and refines the concepts of dependability and security of computing systems, introduced in the seminal work of Avizienis et al., to blockchains and defines a methodology for the engineering and the operation of critical blockchain-based applications. Crypto- Labo, a business-critical application, use case coming from EDF (Electricite ́ de France) business based on the Hyperledger Fabric blockchain, is then introduced and the application of our methodology is sketched.