Place the top oven rack in the center position and pre-heat oven to 400°F.
Place potatoes and garlic in a large pot and add water until the potatoes are completely covered, with an additional inch or two on top. Bring to a rapid boil over high heat for 15 minutes, or until the potatoes are fork tender. Remove from heat, drain, and set aside.
While the potatoes are boiling, add the beef, rosemary, and Worcestershire sauce to a 10” cast iron skillet set over medium heat. Season with salt and black pepper, to taste, and stir to combine. Cook, stirring frequently, until the beef is completely browned and broken into small pieces, approximately 8-10 minutes.
Remove skillet from heat and carefully drain any excess fat from the skillet, if necessary. Set aside.
Add chicken stock, heavy cream, and butter to the boiled potatoes. Season with salt and black pepper, to taste, and mash with a hand masher or whip with a hand mixer until smooth. If necessary, add a little extra chicken broth to reach the desired consistency. Set aside.
Evenly spread the thawed corn, peas, and carrots across the browned ground beef in the cast iron skillet. Top with an even layer of the mashed potatoes and sprinkle with some smoked paprika.
Place the skillet in the pre-heated oven and bake for 30 minutes, or until heated through and the potatoes are nicely browned on top. Remove from oven and cool slightly. Serve immediately garnished with fresh chives. Enjoy!
For best results, use a plastic spatula to cut and serve this dish. If using metal, as shown, be careful not to nick the protective seasoning on your skillet while cutting.