Place bread in a food processor; pulse 5 times or until crumbly.
Add the breadcrumbs, water, and bouillon cube. Reduce heat; simmer 20 minutes. Discard bay leaf.
Place about 2 1/2 cups mushroom mixture in a blender; process until smooth.
Pour pureed soup into a large bowl. Repeat procedure with remaining mushroom mixture, 2 1/2 cups at a time. Stir in 1/2 teaspoon salt and half-and-half. Top each serving with 1 teaspoon chives.