Boil potatoes in a medium pot of salted water until cooked and soft.
Drain and mash with chicken broth, sour cream, 1/2 tsp salt, and pepper, set aside.
Preheat oven to 400°F.
In a large sauté pan brown meat over medium to high heat, breaking the meat up with a wooden spoon as it cooks. Season with 1/2 tsp salt and pepper to taste. I drained the liquid off and used a fork to break it up more.
When cooked, set aside on a plate.
Add the oil, onion, mushrooms, and celery and sauté on medium heat about 5 to 7 minutes, until the vegetables are tender.
Add the flour, frozen or fresh vegetables, beef broth, tomato paste, Worcestershire sauce, rosemary, thyme, cooked meat and mix well. Simmer on low about 8-10 minutes.
Spread the meat on the bottom of casserole dish. Top with mashed potatoes and sprinkle with paprika. ( I added a sprinkle of Cheese to the topping)
Bake 20 to 25 minutes, then place under the broiler 1 to 2 minutes until the potatoes turn golden.
Remove from oven and let it cool 5-10 minutes before serving.