Place the ground beef in the Instant Pot. Break it up into small pieces. Add onion, worcestershire, garlic, thyme and broth. Stir everything together. Place trivet on top of the beef mixture.
Add peeled and chunked potatoes on to the trivet. Close lid, cook on High pressure for 12 minutes. Once cooking time is complete, quick release the pressure.
Remove the potatoes and mash with preferred ingredients in a separate bowl; butter, milk, sour cream etc. Add the cornstarch slurry, salt, pepper, and frozen vegetables to the Instant Pot.
Stir until the mixture has thickened. Scoop the beef/vegetable mixture into a baking dish (I used a 9x9 dish). Top with mashed potatoes. Broil on high for a few minutes or until the top is golden brown.
Remove and garnish with additional thyme, if desired