Heat a large dutch oven over medium/high heat. Add butter.
When the butter is melted add the onion, shallot, and mushrooms to the dutch oven and let the vegetables sauté for 4-5 minutes or until the white onion starts to brown.
Add the garlic to the dutch oven and sauté for an additional 2-3 minutes.
Deglaze the pan with the white wine. Use a spatula to scrape the browned bits from the bottom of the dutch oven.
Add the parmesan rinds, fresh thyme, parsley, water, and sea salt to the dutch oven and stir and bring to a boil.
Turn the heat to low and let the broth simmer for 4-6 hours (the longer the better).
When the broth has simmered and is flavorful add the lemon juice and stir.
Place a large bowl or pot in the sink and set a sieve on top of the pot.
Pour the parmesan broth through the sieve so that all the vegetables, herbs, etc. are caught and the broth below is caught by the bowl.
Use the parmesan broth in soup, sauces, or risotto.