A method for conversion of digital assets to fiat currency using a secondary blockchain and mirrored accounting includes: receiving transaction data corresponding to a first blockchain transaction processed using a first blockchain, the transaction data including a payer identifier, recipient identifier, and blockchain currency amount; validating an entity as an authorized entity associated with the payer identifier; determining a fiat currency amount based on the blockchain currency amount; generating a second blockchain transaction, the second blockchain transaction including an unspent transaction output, destination address associated with the authorized entity, and the blockchain currency amount and/or the fiat currency amount; confirming addition of the second blockchain transaction to a second blockchain; and initiating a transfer for the fiat currency amount from a first transaction account to a second transaction account, the second transaction account being associated with the authorized entity.