Shepherd's Pie

From Every Day with Rachael Ray April 2008

2 pounds small yellow-fleshed potatoes, halved
2 tablespoons extra-virgin olive oil
10 ounces cremini mushroom slices
2 carrots, cut into 1-inch pieces
2 parsnips, cut into 1-inch pieces
1 onion, chopped
1 pound 93-percent lean ground beef
1/4 cup flour
1 1/2 cups beef broth
1/2 cup canned crushed tomatoes
Salt and pepper
3/4 cup 2-percent milk
1 1/2 pounds baby spinach

In a large saucepan, combine the potatoes and enough salted water to cover by 1 inch. Bring to a boil, then lower the heat and simmer until tender, about 15 minutes. Drain and return to the pot; cover.
In a large, deep skillet, heat 1/2 tablespoon olive oil over high heat, add the mushrooms and cook, stirring, until browned, about 5 minutes. Arrange in a greased 9-by- 13-inch baking dish in an even layer.
In the same skillet, heat 1 tablespoon olive oil over mediumhigh heat. Add the carrots, parsnips and onion and cook, stirring, until crisp-tender, 6 to 7 minutes. Add the beef and cook, breaking it up, until no longer pink, about 4 minutes. Stir in the flour. Add the beef broth and tomatoes and simmer, stirring, until thickened, about 5 minutes; season with salt and pepper. Ladle the meat mixture over the mushrooms. Reserve the skillet.
Position a rack in the upper third of the oven and preheat to 400°. Add the milk to the potatoes and mash. Season with salt and pepper.
In the reserved skillet, bring 1 cup water to a boil. Add the spinach and cook, turning, until wilted, about 2 minutes; season with salt and pepper. Transfer to a colander; press to extract any liquid.
Arrange the spinach over the meat mixture, then spoon the potatoes on top. Drizzle with the remaining 1/2 tablespoon olive oil. Bake until golden, about 25 minutes.