4 tablespoons (1/2 stick) unsalted butter
2 shallots, minced
1 clove garlic, minced
20 ounces fresh cultivated mushrooms, such as white button or cremini
12 ounces fresh wild mushrooms, such as morel, chanterelle, or porcini
1/2 cup port, preferably white port
1 cup chicken stock
3 cups water
Salt and pepper to taste
2 tablespoons finely chopped chives
2 tablespoons sherry

Chop cultivated and wild mushrooms together.  Cut them any size you like, as long as they fit in a spoon when finished (remember that they will shrink while cooking).  Small mushrooms may be used whole.
In a large pot over medium heat, melt butter.  Add shallots and garlic, season, and cook until translucent and soft, about 3 minutes.  Lower heat and add all mushrooms.  Season, cover, and sweat, stirring occasionally, until mushrooms are soft and fragrant, about 20 minutes.
Add port to the pot.  Use a wooden spoon to loosen any brown bits from the bottom of the pot.  Raise heat to medium and cook 5 to 7 minutes, until very little port is visible.  Add chicken stock and water, bring to a boil, then remove pot from the heat.  Steep uncovered for 20 minutes.  Season with salt and pepper to taste.
Ladle bouillon into soup bowls and garnish with chives.  Float several dashes of sherry on the surface of each bowl of bouillon.  Serve immediately.