Preparing the Mashed Potatoes:

1. Fill a medium pot with water and add a generous amount of salt. Bring to a rapid boil over medium-high heat.
2. Add the cut potatoes to the boiling water and cook for 7 to 8 minutes, or until they can be easily pierced with a fork.
3. While the potatoes are boiling, heat the butter and milk together in a small saucepan over medium heat until the butter is melted. Alternatively, you can microwave them together in a microwave-safe bowl in 30-second intervals, stirring in between, until the butter is melted.
4. Once the potatoes are tender, drain them thoroughly and return them to the pot.
5. Mash the potatoes to your desired consistency using a potato masher or fork. Gradually stir in the butter-milk mixture until fully incorporated.
6. Season the mashed potatoes with garlic powder, salt, and freshly cracked black pepper. Stir well to combine, then set aside, keeping them warm until ready to serve.

Preparing the Ground Beef and Gravy:

1. In a small bowl, whisk together the cornstarch and ¼ cup of the beef broth until smooth. Set aside.
2. Heat a large skillet over medium heat. Add the ground beef and cook, breaking it apart with a spoon, until browned and no longer pink. Drain any excess fat.
3. Add the chopped onion, garlic powder, salt, and freshly cracked black pepper to the skillet. Stir to combine and cook for about 5 minutes, or until the onion is tender.
4. Pour in the remaining 1¾ cups of beef broth and bring the mixture to a simmer.
5. Slowly add the cornstarch mixture to the skillet, stirring constantly to prevent lumps. Increase the heat slightly and bring the mixture to a boil. Cook for about 2 minutes, or until the gravy has thickened.
6. Taste and adjust the seasoning as needed.

Serving:

1. Spoon the mashed potatoes onto plates or into bowls.
2. Top with the ground beef and gravy mixture.
3. Garnish with chopped fresh parsley, if desired.