Add potatoes to large pot and cover with cold water. Bring to a boil over medium-high heat and cook until tender (about 15-20 minutes.) Drain well. Set aside.
In a small saucepan melt 4 Tblsp of the butter. Add garlic and saute until softened (1-2 minutes). Remove from heat, then stir in the half & half.
Put drained potatoes into a large mixing bowl. Mash well, then mix in seasoning packet and garlic mixture.
Let mixture cool for 5 minutes, then quickly stir in egg yolks one at a time with a wooden spoon. Let mixture cool longer if it is too runny. If mixture is too thick you may add more half & half a little at a time until desired consistency is reached.
Line a baking sheet with parchment paper. Transfer mashed potato mixture into a large piping bag and pipe into 12 mounds spaced evenly apart.Bake for 16-19 minutes or until edges are golden brown.