Heat oil in 8-quart stockpot on high heat. Add mushrooms, leeks and garlic; cook and stir until vegetables begin to brown. Deglaze with wine, scraping browned bits from bottom of pan.
Add stock, peppercorns, sage, sea salt and thyme; bring to boil. Reduce heat to low; simmer 1 hour.
Strain broth through fine mesh strainer. Discard solids. Stir lemon juice into broth. Season with salt and pepper, if desired. Pour broth into beverage glasses or mugs. Drizzle each with 1 teaspoon of the avocado oil just before serving.