Kerm-e Gharch (کرم قارچ) — Persian Cream of Mushroom Soup

• 700 gCremini mushrooms, cleaned and thinly sliced (Or a mix of cremini and white button; slice 4–5 mm thick)
• 200 gYellow onion, finely diced (About 1 large onion)
• 12 gGarlic, minced (About 4 cloves)
• 60 gUnsalted butter (Divided)
• 15 mlOlive oil (Helps prevent butter from browning too quickly)
• 30 gAll-purpose flour (About 1/4 cup; for a light roux)
• 1000 mlChicken broth or vegetable broth (Low-sodium preferred)
• 240 mlHeavy cream (At least 35% fat)
• 4 gFresh thyme leaves (About 1 tablespoon leaves, or 4–5 sprigs stripped)
• 8 gSea salt (Start with 1 1/4 teaspoons, then adjust to taste)
• 2 gBlack pepper, freshly ground (About 1 teaspoon, or to taste)
• 10 mlLemon juice (Optional, to brighten at the end)

Instructions

1. 1

   Prepare the vegetables: wipe mushrooms with a damp towel and slice 4–5 mm thick. Dice the onion finely and mince the garlic. Warm the broth in a saucepan or microwave until hot (about 70–80°C / 160–175°F); adding hot broth helps the soup thicken smoothly and prevents lumps.

2. 2

   In a heavy pot over medium heat, melt 30 g butter with the olive oil. Add the onion and cook 8–10 minutes, stirring often, until soft and translucent but not browned. Add the minced garlic and cook 45–60 seconds until fragrant; keep the heat moderate so the garlic does not scorch.

3. 3

   Add the sliced mushrooms and 1/2 teaspoon of the salt. Increase heat to medium-high and sauté 10–12 minutes, stirring and scraping the bottom, until the mushrooms release their liquid and it mostly evaporates. Continue cooking until the mushrooms begin to brown lightly for deeper flavor.

4. 4

   Reduce heat to medium. Push mushrooms to one side and melt the remaining 30 g butter in the cleared space. Sprinkle in the flour and stir continuously for 2 minutes to cook out the raw flour taste, forming a pale roux. Mix the roux into the mushrooms until everything looks evenly coated.

5. 5

   While stirring, slowly pour in about 250 ml of the hot broth to create a smooth slurry, then add the remaining broth in 2–3 additions. Bring to a gentle simmer over medium heat (small bubbles, not a rolling boil). Simmer 12–15 minutes, stirring every 2–3 minutes, until slightly thickened.

6. 6

   Turn heat to low. Stir in the heavy cream, thyme leaves, remaining salt, and black pepper. Keep the soup at a very gentle simmer for 3–5 minutes (do not boil after adding cream) until velvety and cohesive. For a smoother texture, blend 1/3 to 1/2 of the soup and return to the pot.

7. 7

   Taste and adjust seasoning. If desired, add lemon juice for brightness. If the soup is too thick, thin with 50–150 ml hot broth; if too thin, simmer 3–6 minutes longer on low, stirring to prevent sticking. Rest off heat for 5 minutes before serving for the best body.