How do you hook up a wall thermostat to a 220v baseboard heater, when the 220v feed goes to the baseboard heater first?

If single line break is acceptable, just run a 2 conductor cable from the baseboard to the single pole tstat and wire it just like a light switch. Mark the white conductor with red tape at both ends. I haven't done electric baseboard for a long time and I'm not up on code requirements with that type of thing. Double line break may be required by now.