1-1/4 lbs. sweet potatoes, peeled, cut in half lengthwise and cut crosswise into 1/2 inch slices
1 cup scallions, white and light green parts only, sliced
2-1/2 cups vegetable or chicken stock
1/4 cup evaporated skim milk
1 cup croutons
Place potatoes in a steamer basket over boiling water. Cover saucepan and steam 15-20 minutes or until tender. Remove from steamer basket and set aside. Combine scallions and half the stock in a heavy saucepan over medium heat. Simmer 10minutes, stirring occasionally. Transfer stock mixture to a food processor or blender. Add cooked sweet potatoes and purée until smooth. Return potato mixture to saucepan. Add remaining stock and bring to a boil over medium heat, stirring frequently. Reduce heat to low and simmer 5 minutes. Season with salt to taste. Serve soup warm or chilled with milk and croutons.