The volatile nature of day-ahead electricity markets means that participants often resort to some form of derivative hedging instrument. One such derivative instrument is a Contract-for-Difference (CfD), specifically available to renewable generators in some jurisdictions to enable them to hedge against their price risk. CfD is a bilateral arrangement between a generator selling into, and an offtaker buying out of, a centrally cleared pool market for electricity. In this arrangement, the generator subsidizes the offtaker when the spot price is high; whereas, the offtaker subsidizes the generator when the spot price is low. This establishes a synthetic bilateral electricity transaction, operating in parallel to the pool market. Embracing CfD to hedge against price risk presents new risks such as counterparty credit, margining, third-party, and legal risks. They also incur high costs and possess underlying process risks. Decentralized Finance - an overarching term representing financial services built on top of a public blockchain - seems to present particularly compelling opportunities in electricity derivatives for these reasons. Therefore, we propose a novel Decentralized Finance instrument: a blockchain-based marketplace governed by a smart contract to act as a mediator between stakeholders mutually enrolled in bilateral CfD arrangements. The employed smart contract structure autonomously and irrefutably enforces the terms of the CfD, underpinned by a novel collateralization and settlement mechanism. This novel approach mitigates the hedging-related and underlying process risks of traditional CfD instruments.