- Melt margarine in a large saucepan over medium-high heat.
- Add scallions and mushrooms; cook until tender, stirring, about 5 minutes.
- Combine flour, garlic powder, pepper, broth and milk in a small bowl; mix until well blended.
- Add flour mixture to saucepan; cook until mixture boils and thickens, stirring constantly, about 10 minutes.
- Add chicken, pimentos and sherry; cook until thoroughly heated, stirring occasionally, about 2 minutes.
- Stir in cheese and add cooked spaghetti; toss gently.
- Yields about 1 cup per serving.