Cover the potatoes with water and cook until fork tender, drain well.
Using a hand masher or mixer, mash the potatoes and add the butter, heavy cream, sour cream, salt and pepper.
While the potatoes are boiling, brown the ground beef.
Add the onion, garlic and thyme to the pan and saute for 2 minutes. Remove the meat from the pan and keep warm.
Melt the butter and stir in the flour, then cook for a minute till it no longer smells raw.
Whisk in the broth and cook till it is thickened, then whisk in the worcestershire sauce, tomato paste, and paprika.
Add the mixed vegetables and simmer for 3 minutes.
Return the meat to the pan, stirring to combine.
Preheat the broiler to 500° and move the rack up to the top of the oven.
Pour the mixture into a 9x13-inch pan. Spread the potatoes evenly over the top and place under the broiler for 5 minutes, or until the top has lightly browned.
Remove and rest for 5 minutes before serving.