I. This is the richer of the two versions. Use in place of beef stock.
Heat in a Dutch oven over medium heat:
Add:
Sauté until starting to brown, about 7 minutes. Add:
Sauté until the mushrooms have softened and released their juices, about 5 minutes. Add:
Stir and allow a dark brown fond (or crust) to develop on the bottom of the pot. Add:
Scrape the browned bits off the bottom of the pot. Add:
Simmer, partially covered, for 45 minutes. Strain, pressing the vegetables with a spoon to extract as much liquid as possible. Cool uncovered, then refrigerate covered for up to 4 days or freeze for up to 6 months.
II. This version is better suited to replacing chicken or pork stock. Use in Hungarian Mushroom Soup, ramen, or Miso Soup.
Preheat a cast-iron skillet over medium-high heat. Place cut side down in the skillet:
Cook until the vegetables are well charred, about 5 minutes. Remove from the heat and set aside. Warm in a pot or large saucepan over medium-high heat:
When the oil shimmers, add and sauté until starting to brown:
Add:
Sauté until the mushrooms start to release their juices, about 5 minutes. Add the charred leek, ginger, and leek tops along with:
Bring to a gentle simmer, partially cover, and cook for 45 minutes. Strain through a fine-mesh sieve, pressing on the solids with a ladle to extract all the liquid. Stir in:
Cool uncovered, then refrigerate covered for up to 4 days or freeze for up to 6 months.