01 - Place all vegetable scraps, optional potato, and fresh vegetables in a large stockpot.
02 - Add bay leaves, parsley, thyme, peppercorns, garlic, salt, and vinegar or lemon juice if using.
03 - Pour in cold water and stir to combine all ingredients.
04 - Heat over high until boiling, then reduce heat to maintain a gentle simmer.
05 - Remove any foam forming on the surface within the first 10 minutes of simmering.
06 - Continue simmering uncovered for 1 hour, stirring occasionally.
07 - Remove pot from heat and allow the liquid to cool briefly.
08 - Strain through a fine-mesh sieve or cheesecloth into a large bowl or container, discarding solids.
09 - Taste the broth and adjust salt or acid if necessary.
10 - Use immediately or refrigerate up to 5 days, or freeze for up to 3 months.