Wash the vegetables, and roughly chop them into large chunks.
Put the carrot, celery, onion, fennel (including fronds), garlic, dried mushrooms, parsley, bay leaves, rosemary, thyme, and water into a large pot. Stir to combine.
Bring the pot to a boil, then reduce heat to simmer, cover, and cook for 2 hours. Remove from the heat, and cool for 30 minutes.
Remove the vegetables from the broth, and strain the liquid to remove any remaining vegetable debris. Pour the broth into jars with lids and store for 2 weeks in the fridge or 2 months in the freezer.