Combine all Cowboy Butter ingredients in a bowl, place on parchment paper and roll into a log. Refrigerate at least 10 minutes before serving.
Cut 3 tablespoons of Cowboy Butter and place into a preheated, cast iron skillet. Add diced potatoes and cook over medium heat for 20 minutes.
Preheat your grill to 250°F for 2-zone cooking.
Add whole milk to potatoes and place skillet in grill. Close the lid and cook over indirect heat for 1 hour at 250°F.
Turn the 2 open burners on high until your grill reaches 350°F. Top potatoes with shredded cheese and crumbled bacon, close the lid and cook for another 5 minutes.