3 cups reduced-sodium chicken broth or vegetable broth
1/4 teaspoon freshly ground black pepper
12 ounces Yukon gold potatoes, quartered
3 cups sliced fresh mushrooms (optional)
2 tablespoons butter
3 cups fresh spinach leaves
3 cups fresh arugula leaves
2 cups fresh Italian (flat-leaf) parsley leaves and tender stems
1 medium ripe avocado
1 cup Fresh arugula
In 3-quart saucepan cook onion and carrots in hot oil over medium heat for 5 minutes. Add broth, pepper, and salt to taste. Bring to boiling. Add potatoes and return to boiling; reduce heat. Simmer, covered, for 10 minutes.
Meanwhile, in a large skillet cook mushrooms in hot butter over medium heat for 6 to 8 minutes or until tender and liquid has evaporated; set aside.
Remove saucepan from heat. Use an immersion blender to blend onion-potato mixture until almost smooth. Add spinach, the 3 cups arugula, avocado and the parsley. Return to heat. Bring to boiling; remove from heat. Using immersion blender, puree soup again until nearly smooth and flecks of green remain. Season to taste with salt. Serve immediately topped with sautéed mushrooms and additional fresh arugula.