Combine the cut biscuit dough with the pepperoni slices and mozzarella cheese in a large bowl. Toss to combine.
Fill each prepared well in the muffin tin with approximately 6 pieces of dough - make sure you are getting the pepperonis and cheese along with it.
Add a thin slice of butter to the top of each portion. (approx ½ tbsp for each)
Bake for 20-25 minutes or until golden brown and bubbly.
Combine the remaining 4 tbsp of butter with the garlic salt and dried parsley. Microwave for a few seconds to melt. Once the butter has melted, whisk to combine the seasonings.
Once the muffins are done baking, remove them and brush them with the melted butter mixture.