Preheat the grill to medium-high heat, about 400-425°F.
Scrub potatoes, pierce with a fork, rub with olive oil and salt, then wrap in foil.
Grill the wrapped potatoes for 45-60 minutes until tender.
In a small saucepan, melt butter over medium heat; add minced garlic and fresh herbs to make garlic herb butter.
Season beef medallions with olive oil, salt, and pepper.
Sear the beef cubes in a hot cast iron skillet for 2-3 minutes per side until browned.
Once potatoes are cooked, cut them lengthwise and fill with sour cream and pepper jack cheese mixture.
Top filled potatoes with seared beef bites and drizzle with garlic herb butter before serving.