Take a small saucepan and add the water to it, along with the sliced mushrooms, seaweed, peeled garlic cloves, tamari sauce, and miso paste.
¼ cup tamari, 1 cup wakame seaweed, 1¼ teaspoons chickpea miso, 4 cloves garlic, 4 cups water
Bring the mixture to a boil, then cover and reduce the heat to a simmer. Simmer 15-20 minutes.
Remove from the heat and allow it to cool to room temperature. Once cool, strain the sauce into a mason jar or other airtight container of your preference.
Notes
If you have time, let the ingredients steep overnight or for up to 24 hours before straining to extract extra flavor.
You can use dried shiitake instead of fresh for a deeper flavor.
You can use soy miso instead of chickpea miso if you prefer.
For a soy-free fish sauce, replace the tamari with coconut aminos.