Slow Cooker 5-Mushroom Barley Soup

3 cups water

1 cup barley

4 cups beef broth

1 cup milk

2 tablespoons olive oil

1 cup diced onion

½ cup diced celery

½ cup diced carrot

1 tablespoon finely chopped garlic

1 (6 ounce) package sliced white mushrooms

½ cup chopped brown beech mushrooms

½ cup chopped oyster mushrooms

¼ cup dried shiitake mushrooms

¼ cup dried black mushrooms, broken into small pieces

1 (10.75 ounce) can condensed cream of mushroom soup

½ teaspoon salt

½ teaspoon ground mixed peppercorns

Heat water in a slow cooker set to High until hot; add barley, beef broth, milk, olive oil, onion, celery, carrot, garlic, white mushrooms, brown beech mushrooms, oyster mushrooms, shiitake mushrooms, black mushrooms, cream of mushroom soup, salt, and ground mixed peppercorns to the slow cooker.

Cover and cook on High for 1 hour.

Remove shiitake mushrooms with a slotted spoon and chop into 1/2-inch pieces. Reduce heat setting to Low and continue cooking 7 hours more.