For the Instant Pot: Brown the ground beef. If browning in the Instant Pot, make sure to use the beef broth to deglaze the pot.
Add the browned ground beef to the Instant Pot liner along with the onion, carrots and beef broth. Season with parsley, salt and pepper.
Peel and cube the potatoes. They should be cut fairly small, approx 1 inch cubes. Add the potatoes to your steamer basket.
Place the steamer basket into the Instant Pot, on top of the beef and carrots.
Cook on Manual HIGH for 3 minutes. Quick release the pressure.
Remove the steamer basket and pour the potatoes into a large bowl. Set aside.
Add the frozen peas and au jus seasoning mix to the Instant Pot. Stir to combine and then place the lid back on. Let the pot sit for 5 minutes.
While the pot is resting, add the butter and sour cream to the potatoes and mash. You can add a splash of milk to your potatoes if you'd like, I like mine thick though.
Turn your Instant Pot onto saute. Carefully remove about 1/4 cup of liquid from the Instant Pot, mix in the cornstarch and then return the cornstarch slurry to the Instant Pot once the broth is boiling.
Stir until thickened. Transfer contents of the Instant Pot to an oven safe dish.
Carefully spread the mashed potatoes onto the beef mixture. Top the mashed potatoes with shredded cheese.
Broil for a few minutes until the cheese is melted and bubbly.
For the Stovetop: Brown the ground beef. Drain the grease.
Add in the carrots, onion, parsley, salt, pepper and broth. Simmer until the carrots are cooked through.
Add the frozen peas and au jus seasoning mix. Simmer for 2 minutes.
Remove 1/4 cup of liquid from the pot. Mix in the cornstarch and return the cornstarch slurry to the pot. Stir to thicken.
In a separate pot, boil the potatoes until fork tender. Mash the potatoes with the butter and sour cream.
Transfer contents of the Pot to an oven safe dish.
Carefully spread the mashed potatoes onto the beef mixture. Top the mashed potatoes with shredded cheese.
Broil for a few minutes until the cheese is melted and bubbly.