Heat a large skillet over medium high heat, then add ground beef and brown until fully cooked.
Soak up excess beef fat with a paper towel, then add onions and carrots and cook for 10 minutes until soft.
Add peas, corn, butter, flour, thyme leaves, and garlic, and stir for 1 minute.
Add beef stock and bring to a boil, then cook for a minute or two until the broth thickens into a light sauce.
Transfer the beef and vegetable mixture to an 8x8 baking dish.
Preheat oven to 425ºF.
Boil the cubed potatoes until fork-tender, then drain.
Mash the potatoes using a fork or potato masher, and stir in cream, milk, butter, and cheddar cheese.
Season the mashed potatoes with salt and pepper.
Spread the mashed potatoes on top of the beef and veggies in the baking dish.
Bake the shepherd's pie for 20-25 minutes, until the mashed potatoes are golden brown and crispy on top.
Serve and enjoy!
