Cut off the top of the garlic bulb, and roast in a preheated 350-degree oven in a ceramic dish for approximately 30 minutes.
Place the red potatoes in a pot of water and boil until tender. Drain and set aside. Take 2 potatoes from the pile, cut them into quarters and place them on a cookie sheet. With a fork smash them down until flat, brush them with a little bit of the melted butter, and cook in a warm oven until crispy and golden brown. Set aside to top the finished potatoes.
Saute the onions in the olive oil until the onions are translucent.
Place the roasted garlic, boiled potatoes, 2 tablespoons butter, and sour cream into a standing mixer fitted with a paddle attachment, and beat until thoroughly blended.
Scoop the potato mixture into a ceramic dish. Drizzle with the remaining melted butter and place in the oven until the top is browned. Push the "potato croutons" into the top of the potatoes and serve immediately.