nonBMPString ::= "𝔘𝔫𝔦𝔠𝔬𝔡𝔢";
encoder ::= a UTF8 encoder;
bytes ::= encoder process nonBMPString;
|bytes|

// or, as a one-liner
|a UTF8 encoder process "𝔘𝔫𝔦𝔠𝔬𝔡𝔢"|