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1
Peel potatoes and cut into cubes.
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2
Place in cold salted water and bring to a boil, reduce heat to low boil until potatoes are fork tender, about 15 minutes.
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3
Drain potatoes and mash with milk and 2 tablespoons of the butter until smooth.
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4
Season with salt and pepper to taste and set aside.
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5
Brown ground beef in a large saucepan over medium-high heat.
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6
Remove ground beef from pan and drain off excess fat, reserving 3 tablespoons of fat.
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7
Put reserved fat in saucepan add onion, carrot, and celery.
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8
Saute for 5 minutes until onion becomes translucent.
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9
Add mushrooms and frozen peas, saute for 5 more minutes.
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10
Return ground beef to pan along with parsley, thyme, Worcestershire, and nutmeg.
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11
Simmer for 1 to 2 minutes.
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12
Add brown gravy to pan, and simmer 1 to 2 minutes more.
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13
Season to taste with salt and pepper.
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14
Remove from heat and let cool.
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15
Preheat oven to 400 degrees.
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16
Layer bottom of a 3-liter casserole dish with beef mixture, top with mashed potatoes, making uneven peaks with a fork.
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17
Cut remaining butter into small cubes and sprinkle over mashed potatoes.
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18
Bake for 30 to 40 minutes, until mashed potatoes have turned golden brown.
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19
Remove from oven and let cool 5 minutes.
