Place the dried shiitake mushrooms in a heatproof bowl and cover with 2 cups (about 480 ml) of warm water. Let soak 20–30 minutes until softened. Reserve soaking liquid by straining through a fine sieve or coffee filter to remove grit; set liquid aside.

Prepare Fresh Vegetables and Mushrooms

While shiitakes soak, wipe cremini and button mushrooms clean with a damp towel and slice them. Roughly chop the halved onion, carrot, and celery. Smash the garlic cloves with the flat of a knife; leave skins on if you prefer a milder garlic note.

Build and Simmer the Broth

Sauté Fresh Mushrooms and Aromatics (optional)

In a large heavy-bottomed pot, heat the olive oil or butter over medium heat. Add sliced cremini and button mushrooms in a single layer and cook 5–7 minutes without stirring too often until they release liquid and begin to brown. Add chopped onion, carrot, celery and smashed garlic and cook 4–5 minutes until softened and aromatic. This step adds depth but can be skipped for a purer clear broth.

Combine Ingredients in Pot

Add the rehydrated shiitake mushrooms (reserve any very large stems to discard), the reserved shiitake soaking liquid (pour carefully, leaving any sediment behind), bay leaves, thyme sprigs, and whole peppercorns to the pot. Pour in the cold water (adjust quantity so all ingredients are submerged—about 3 liters total).

Simmer Slowly

Bring to a gentle boil over medium-high heat, then immediately reduce to a low simmer. Partially cover and simmer for 90–120 minutes. For an even richer flavor, simmer up to 3 hours. Skim any foam or impurities from the surface during the first 30 minutes.

Season During Cooking

About 30 minutes before finishing, add sea salt and 1 tablespoon soy sauce or tamari. Taste after 20–30 minutes and adjust salt or soy sauce to preference—broth should be savory and well-rounded but not overly salty.

Finish, Strain and Enhance

Strain the Broth

Remove from heat. Use a slotted spoon to remove and discard large solids (bay leaves, thyme sprigs, large mushroom pieces you don’t want). Strain the liquid through a fine-mesh sieve or cheesecloth into a clean pot or bowl to produce a clear broth. Press gently on solids to extract more liquid, but avoid forcing too much sediment through.

Optional Enrichments

Return strained broth to low heat. If you want a deeper umami, whisk in 1 tsp white miso dissolved in a small amount of warm broth (off heat to preserve probiotics) and/or the remaining 1 tablespoon soy sauce. For a creamier soup, stir in up to 1 cup heavy cream or coconut milk and warm through without boiling. Add 1 tsp lemon juice to brighten flavor and 2 tbsp chopped parsley for freshness.

Final Adjustments and Serve

Taste and adjust seasoning with salt, soy sauce, or a few grindings of black pepper. Serve hot as a clear mushroom broth or use as a base for mushroom soup, ramen, risotto, or sauces. Broth will keep in the refrigerator for 4–5 days or frozen for up to 3 months.