Heat a large skillet (I prefer nonstick here) over medium high heat, then add beef. Brown beef until fully cooked, about 5 minutes (I find there’s enough fat released in the beef that I don’t need to add oil to the pan). Soak up excess beef fat with a paper towel, then add onion and carrot. Season with a pinch of salt and pepper, then cook for 10 minutes, until soft.Add the peas and corn, and cook for 2 minutes. Add butter to the pan and toss around until fully melted, then stir in flour, thyme leaves, and garlic. Stir for 1 minute, until flour disappears. Add beef stock, then bring liquid to a boil over high heat. Cook for a minute or two until broth thickens into a light sauce. Remove pan from heat and transfer beef and veggie mixture to an 8x8 baking dish.Preheat oven to 425ºF.To make the mashed potatoes, place cubed potatoes in a pot filled with cold water. Place on the stove set over high heat and bring to a boil. Cook for about 5 minutes, until potato cubes are fork-tender. Drain potatoes, then spread them out on a sheet pan in a single layer and let sit for a couple minutes so the steam can escape. Use a fork or potato masher to mash the potatoes, then stir in cream, milk, butter, and cheese. Make any necessary seasoning adjustments with salt and pepper. Spread mashed potatoes on top of the beef and veggies in the 8x8 baking dish.Bake shepherd’s pie for 20–25 minutes, until mashed potatoes are golden brown and crispy on top. Serve and enjoy!Freezer Instructions: After baking, let pan cool to room temperature, then cover tightly with foil and place in the freezer for up to 2 months. When ready to eat, reheat the shepherd's pie (still covered with the foil) for 1 hour in a 350ºF oven. If you thaw the pie in the fridge the night before, you can cut that time in half.