Step 1

Scrub the potatoes under cool water; peel (you do not need to peel if using Yukon golds). Chop into 1-inch pieces and place in a pot of cold water.

Step 2

Place the pot on the stove and bring to a boil over high heat. Boil potatoes for 12-15 minutes, until very tender when pierced with a fork, but not falling apart. (While the potatoes cook, you can prepare the meat filling.) Transfer potatoes to a colander and drain well.

Step 3

Return potatoes to the empty pot or place them in a large bowl. Add the butter pieces to the potatoes in the pot. Use a potato masher or hand mixer to mash the potatoes.

Step 4

Add the milk, sour cream, salt and pepper. Stir or mix with a hand mixer. Taste and adjust seasonings as needed. Set aside.

Step 5

Preheat oven to 400° F.

Step 6

Heat a large skillet over medium-high heat. Add the ground beef and chopped onion to the pan and cook, breaking up the meat, until the beef is browned. Drain off excess grease.

Step 7

Reduce the heat to medium. Add the garlic, frozen vegetables, flour and tomato paste. Cook stirring, for 1-2 minutes.

Step 8

Add the beef broth, Worcestershire sauce, paprika, thyme, salt and pepper. Stir. Bring to a low simmer and cook for 10 minutes (reduce the heat as needed to keep it at a low simmer), until most of the liquid is gone. If the meat looks dry, you can add a little more broth. You want it to have some moisture, but do not want it soupy. Then remove pan from the heat.

Step 9

Transfer the meat mixture to a 9x13-inch baking dish. Spoon the mashed potatoes over the top and then spread into an even layer. Use a fork to make some textured ridges on the mashed potatoes; these will crisp and brown in the oven.

Step 10

Bake uncovered for 25-30 minutes until potatoes are golden brown on the edges. (Place a rimmed baking sheet on the rack below to catch any drips.) If desired, broil for 1-3 minutes to brown the potatoes in spots. Let stand for 5 minutes and then serve.