Preheat your oven to 375°F.
Return the same pot used to boil the potatoes to the stove and place on medium heat.
Add in one pound of ground beef. Brown the meat and break it up as it cooks using a wooden spoon.
When the meat is still slightly pink, add the diced onion, garlic, and carrots. Season with a 1/2 teaspoon of salt and 1/4 teaspoon of pepper (or season to your liking). Continue to cook for another 8 minutes.
Dice the peeled roasted green chiles. (See notes.)
Cook for another 4-5 minutes until meat is cooked through and carrots are slightly tender. Taste for seasoning and adjust salt and pepper as needed.
Add the meat mixture to a medium baking dish (about 2.5 quarts) and spread evenly throughout the bottom. Spoon the mashed potatoes all over the top and carefully spread until all the meat mixture is covered.
Bake in the oven for 20-25 minutes. You can turn the broil on during the last 3-4 minutes to let the top brown slightly.
Cut into slices and serve.