Prepare the Steaks:
Remove steaks from the refrigerator 30 minutes before cooking.
Pat them dry with paper towels.
Brush each steak with olive oil and season generously with salt and pepper. Add optional garlic powder and rosemary if desired.

Prepare the Mashed Potatoes:
Peel and chop the potatoes into equal-sized chunks.
Place them in a large pot and cover with cold water. Add a pinch of salt.
Bring to a boil over medium-high heat, reduce to a simmer, and cook for 15-20 minutes until fork-tender.
Drain the potatoes and return them to the pot.
Add butter and gradually mash potatoes with a potato masher or fork.
Slowly add milk or cream, mixing until smooth and creamy.
Season with salt and pepper to taste.

Grill the Steaks:
Preheat a grill pan or outdoor grill to medium-high heat.
Grill steaks for about 4-5 minutes on each side for medium-rare, or until desired doneness is reached.
Remove steaks from the grill and let them rest for 5 minutes before serving.

Plating:
Place a generous scoop of mashed potatoes on a plate.
Arrange the grilled steak next to the mashed potatoes.
Garnish with freshly chopped parsley.