public ProcessableBlockHeader buildProcessableBlockHeader() {
    validateProcessableBlockHeader();

    return new ProcessableBlockHeader(
        parentHash,
        coinbase,
        difficulty,
        number,
        gasLimit,
        timestamp,
        baseFee,
        mixHashOrPrevRandao,
        parentBeaconBlockRoot);
  }
A utility class for building block headers.
ethereum/core/src/main/java/org/hyperledger/besu/ethereum/core/BlockHeaderBuilder.java