Cheddar Topped Shepherd's Pie

I saw this recipe on Martha Stewart's site, and it looked yummy!  My family loves potatoes and beef but we haven't tried any shepherd's pie, ever.  But beef and potatoes we love, so I gave it a try.  Although I made some adjustments from the original recipe called for.

Ingredients:
4 medium potatoes, peeled and sliced
1 tbsp vegetable oil
1 medium carrot, halved lengthwise
1 celery stalk, thinly sliced
1 large onion
1/2 tsp dried thyme
1/4 cup all purpose flour
1/4 cup tomato paste
2 pounds ground beef
1 cup whole milk
1 1/2 cups shredded cheddar cheese
1 cup beef stock
salt and pepper

Preheat oven to 450.  Boil potatoes with salt in a saucepan and cover.  Cook until potatoes are easily pierced with a tip of a paring knife.
Meanwhile, heat oil in a heavy pot over medium-high.
Add carrots, celery, onion and thyme.  Cook, stirring occasionally until vegetables are tender about 8-10 mins.
Add flour and tomato paste, cook, stirring, 1 minute.
Add beef, cook, stirring occasionally, until no longer pink, 6-8 minutes.
Add the beef stock bring to a boil and simmer, about 1 minute.  Set aside.
Drain potatoes, return to pan, cook over medium stirring until liquid evaporated and a thin film covers bottom of pan.
Remove pan from heat, add milk and 1 cup cheddar cheese.
Mash until smooth, season cheddar potato with salt and pepper
Pour beef filling into a 13 by 9 inch baking dish.  Drop dollops of topping over filling, spread to edges with a spatula.  Sprinkle with remaining cheese.
Bake until topping is browned and filling is bubbling rapidly, about 20 minutes.  Let stand 5 minutes before serving.

Enjoy! :))