I made this recently with freshly ground lamb from the farmer's market, and it was SO good! I usually just use ground beef, and I never get any complaints. You can change up the veggies in this or even the meat so that it is perfect for your family's taste. Enjoy!
Preheat oven to 400F. Brown the ground lamb/beef in a frying pan with the onions, seasoning with salt and pepper. While the meat is browning, boil the potatoes in one pot and the carrots in another. After boiling the carrots for 5 minutes add the peas.
When the meat is finished, remove carrots and peas from heat and drain. Add the gravy to the meat mixture. After the gravy is completely mixed in, add the peas and carrots.
When potatoes are just soft enough to mash, drain and combine with cheese, milk, and yogurt/sour cream, and season with salt and pepper to taste. Use a beater or mash really well to get potatoes nice and smooth. Add egg white to mixture towards end.
Put meat mixture in the bottom of a medium sized casserole dish. Put the mashed potatoes on top. Make sure each layer is even.
Bake shepherd's pie in the oven for about 40 minutes, until the gravy is bubbly and the potatoes start to brown.
Remove from oven. Let sit about 10 to 15 minutes. Enjoy!