Slice the baby bella mushrooms. Chop the carrot and celery.
Add the fresh and dried mushrooms, carrot, celery, water, and salt to a saucepan and bring to a simmer. Simmer for 15 minutes.
Strain out the vegetables. You can save the fresh mushrooms and eat them; just add salt or sauté them in butter! Use immediately, refrigerate for 1 week or freeze in a freezer safe container for up to 6 months.