Start frying bacon in pan.
Place clean watercress in a bowl and add croutons (as many as you prefer)
When bacon has finished cooking add olive oil, parsley, and vinegar to the pan.
Remove from heat and stir oil, bacon, parsley, & vinegar. Cool briefly.
Add bacon & oil mixture to watercress. Toss to coat.
If desired, add a splash of balsamic vinegar to the top of the salad.