Trying to create a count up timer for a laundy cycle that displays in minutes:seconds

Configuration
12

it’s not about counting but about how often your counter increments.
if you increment it every second like

trigger:
  - seconds: /1
    platform: time_pattern

you’ll have seconds in your counter.
then you will probably need a template sensor that displays it in minutes:seconds and that’s exactly where you’ll need your tempting skills - have a look here and here.