Mashed Potatoes with Shiitake Mushroom Gravy

2 pounds russet potatoes (4 to 5 medium)
1/3 to 2/3 cup half-and-half or whole milk
1/4 cup butter
1/4 cup plain yogurt
1/2 teaspoon salt
1/4 teaspoon ground black pepper
3/4 cup thinly sliced green onion or 1/3 cup snipped fresh chives
3 tablespoons butter
1/4 cup finely chopped onion
2 cloves garlic, minced
1 pound fresh shiitake mushrooms, stemmed and sliced
1/3 cup beef broth
1/3 cup madeira or beef broth
2 tablespoons snipped fresh tarragon
1/4 teaspoon salt
1/4 teaspoon ground black pepper
2 tablespoons whipping cream
Directions

1. Peel and quarter potatoes. In a covered large saucepan, cook potatoes for 20 to 25 minutes or until tender in enough boiling, lightly salted water to cover; drain.

2. Mash with a potato masher or ricer or beat with an electric mixer on low speed. Add 1/3 cup of the half-and-half and the 1/4 cup butter, stiring until nearly smooth. Stir in yogurt, the 1/2 teaspoon salt, and 1/4 teaspoon pepper. If necessary, gradually mash in enough of the remaining 1/3 cup half-and-half to make mixture light and fluffy. Stir in green onion.

3. For mushroom gravy, in a medium saucepan, heat the 3 tablespoons butter over medium heat. Add onion and garlic; cook and stir for 1 minute. Add mushrooms; cook just until mushrooms are tender, stirring occasionally. Stir in broth, madeira, tarragon, 1/4 teaspoon salt, and 1/4 teaspoon pepper. Cook about 3 minutes or until mushrooms are tender, stirring occasionally. Stir in whipping cream. Simmer, uncovered, for 2 minutes more.

4. To serve, spoon mashed potatoes into a serving bowl. Make a depression in the center; spoon mushroom gravy over potatoes. Makes 8 servings