Converting reality to Petri net
I'm not sure how to approach your particular problem, but here is an attempt.

Consider the recipe you are using as a collection of steps, some of which depend on others; for a salad you might have "make dressing", "shred lettuce", "slice cucumber" etc. The dependencies are given through resources, which here are ingredients, possibly in some processed state, like oil, vinegar, cucumber, sliced cucumber, etc.

To model this process as a Petri net, you use


places to represent the various resources, i.e. you have a "vinegar" place, a "shredded lettuce" place, etc,
tokens on those places to represent the amount of each resource you have; initially this would be something like one token on each unprocessed ingredient,
transitions to model actual steps in the recipe; for example you could have a "make vinaigrette" transition consuming a token from the "oil" and "vinegar" places and producing a token in the "dressing" place.


The amount of detail here depends on what you want to do with the model; you might for example want to keep track of equipment in addition to ingredients (with the "make vinaigrette" transition additionally consuming a clean whisk and producing a used whisk), etc.

Is this the kind of example you had in mind?