Add the potatoes and 1 tablespoon salt to a large pot of water, making sure potatoes are submerged under the water.
Bring to a boil and cook potatoes until fork tender, 20-30 minutes.
Drain potatoes and allow them to steam dry. Set aside.
In the bowl of a stand mixer, combine softened cream cheese and half the softened butter. Whip together on high speed until fluffy, about 2 minutes.
Add the still warm potatoes to the mixing bowl. Turn mixer to low speed and slowly add half & half, a little at a time. Once combined, add the minced garlic, parsley, Ranch dressing mix, pepper, and salt to taste. Whip until blended.
Spoon potato mixture into a greased casserole dish.
Cover with foil and refrigerate overnight or for up to 2 days.
When ready to bake, set out casserole for 1 hour to allow it to come to room temperature.
Preheat oven to 350°F.
While oven preheats, remove foil from casserole dish.
Using the back of a spoon create divots in the top of the casserole.
Place pats of melted butter into each of the divots you made with the spoon.
Recover casserole dish with foil and bake for 45 minutes.
Remove foil and bake for an additional 15 minutes until slightly toasted along the edges.
Garnish with minced chives if desired.