Shepherds Pie

I really don't like normal shepherds pie with the tomatoe sauce, but Cory does. I looked for quite some time and found this one that we both really like.
I got this from food network and addapt it as I go. Substitute what you have and it still comes out good.

Ingredients
1/4 cup unsalted butter
1 pound ground or shredded beef
1 cup chopped yellow onions
2 carrots, chopped
1 1/2 teaspoons salt
1 teaspoon ground black pepper
4 ounces button mushrooms, wiped clean and sliced
1 bay leaf
2 tablespoons all-purpose flour
1 tablespoon tomato paste
1 1/4 cups lamb orbeef stock
1 teaspoon Worcestershire suace
1 pound potatoes
1/8 teaspoon ground nutmeg
1/2 cup heavy cream or use milk and add a teaspoon of butter

1/2 cup white cheddar, grated
Directions
Lightly grease a 6-cup baking dish and set aside.
Melt 2 tablespoons of the butter in a large saute pan over medium high heat. Add the meat and cook until starting to brown, about 3 minutes. Add the onions, carrots, 3/4 teaspoon salt, and 1/2 teaspoon of the pepper, and cook, stirring, for 2 minutes. Add the mushrooms and bay leaf, and cook, stirring, until their liquid is almost all gone, about 4 minutes. Add the tomato paste and cook, stirring, until starting to color, about 1 to 2 minutes. Add the flour and cook, stirring, for 1 minute. Gradually add the stock and Worcestershire sauce, and bring to a boil. Reduce the heat to medium-low, cover, and simmer until thickened, about 20 to 25 minutes.
Preheat the oven to 400 degrees F.
Meanwhile, place the potatoes in a medium pot and cover with salted water by 1-inch. Bring to a boil and cook until tender, about 10 minutes. Drain in a colander and return to the pot. Over low heat, mash the potatoes with a potato masher. Add the remaining 2 tablespoons of butter, 3/4 teaspoon of salt, 1/2 teaspoon of pepper, and nutmeg, and mash to incorporate. Add the heavy cream and mix well. Remove from the heat.
Remove the pot with the meat from the heat. Remove the bay leaf. Spoon into the prepared dish and top with the mashed potatoes, smoothing the top. Sprinkle the cheese over the top and bake until browned and bubbly on top, 10 to 15