Obviously a 60V reference is unavailable at powerup. Therefore you must arrange things so that switching occurs continuously, regardless of output level. (This is a quirk of boost converters.)
Divide down the 60V so it creates a usable feedback signal. Options might be an optocoupler, and/or zener diode to create expanded scale measurement.
You must start operating at a duty cycle that you have found is guaranteed to result in 60V output. Eventually you want feedback to start its action when output is in the vicinity of 60V. Therefore make needed design adjustments in gain, threshold, envelope, etc.