Chop apples into medium chunks and slice onions to be about ¼ - ½ inch thick. Set aside.
In a small bowl, mix honey, mustard, salt, pepper, and parsley. Whisk and set aside.
Place one 8-12 inch piece of foil on your work surface. Put another piece over the top to create a cross shape. Place ½ tbsp butter in the center of the foil. Place the pork in the middle of the foil.
Top the pork with ¼ of the onions and ¼ of the apples.
Spoon a tbsp of dijon sauce over the apples and onions. Top with ½ tbsp butter. Close the foil packet by bringing opposites sides together and sealing.
Heat grill to 375°F. Place packets on the grill and for about 30 minutes. Remove and carefully open because the inside will be hot. Serve.