Fill a large stock pot with plenty of water. Add the chopped potatoes and make sure the water covers them.
Bring to a boil, covered, over high heat. Reduce the heat to medium and continue boiling for about 20-25 minutes, until the potatoes are fork tender.
Drain the potatoes and return to the pot.
Add 1/2 cup butter. Mash with a potato masher or mixer until they are as smooth as you like them.
Stir in sour cream, milk, 1 teaspoon salt, 1/2 teaspoon pepper, seasoning salt, garlic powder, and onion powder. All seasonings are to taste. Cover and set aside.
In a large skillet, melt 4 tablespoons butter over medium heat.
Add the onions and carrots. Saute for about 8 minutes, until the carrots are tender.
Add the ground beef and cook and crumble until no longer pink, about 5-6 minutes.
Drain the fat.
Add the frozen peas.
In a small bowl, stir together beef broth* and cornstarch.
Add this mixture to the meat, as well as the Worcestershire sauce.
Cook over high heat for about 5 minutes, or until the mixture boils and the sauce has thickened. Cook and reduce until it has reached a consistency you like.
Season with salt and pepper. Taste it and see how you like it! Add other seasonings if you want.
Preheat your oven to 350 degrees F.
Pour the meat mixture into a deep 9x13 inch casserole dish.
Top with the mashed potatoes and spread evenly.
Top with cheddar cheese.
Bake at 350 for about 30 minutes, or until bubbly. (You could do 375 if you are in a hurry. Check it at 20 minutes.)
Broil on the top rack for about 2 minutes if you are obsessed with crunchy brown cheese like my family is. Don't walk away!!
Now invite over the neighbors. Because this pie feeds a crowd!