Shepherd's Pie 2014 St Patty's with Lamb

Shepherds to not shepherd cattle. They herd sheep...  Also, I prefer a meat based gravy to the tomato based sauce.  In a hurry, I'll use jarred gravy, rather than tomato paste / sauce.
It makes for a totally different flavor.

2 Lbs Lamb
1 + 1/2 chopped onion (about 1+ cup)
1/2 Lb Carrots sliced thin (about 1 c. chopped)
1/2 Lb Frozen Peas  (about 1 c. chopped)
4 cloves of garlic
1 C Beef broth (I could not find my frozen lamb stock, I must have used it all.)
2 TBS Worcestershire
1 TBS oil.
1 -2 TBS flour
1/2-1 tsp salt, 1/2-1 tsp pepper, 1/2 tsp rosemary, 1/2 tsp thyme

5 Lbs Potatoes (Only used about three, but leftover mashed, mmm)

1 C Half and Half or Milk

1/4 C Sour Cream

1 Stick of Sweet Butter

1/2 tsp salt

1/2 C grated Cheddar cheese

Preheat oven to 400

Peel and chop the potatoes into 1/2-1" cubes.  Boil in salted water.

Brown the lamb in oil, adding all the spices including Worcestershire sauce.
Remove lamb from pan with a slotted spoon when browned.
Saute the onion and carrots 3 minutes in the leftover juices/oils. Add the garlic, 1 minute more.
Add back the meat, sprinkle in the flour, coating the meat, cooking it and thickening the sause
Add beef broth (use the leftover potato water to make a thicker beef broth from base.)
Simmer until sauce thickens.

Mash the potatoes adding salt, butter, half and half, sour cream, until smooth and creamy.

Place meat filling in casserole.
spread the potatoes over the meat filling
sprinkle with grated cheese.

Bake 20-25 until browned.