Boil the cut, peeled Yukon gold potatoes until fork tender (about 20-25 minutes in a large pot.
Strain the potatoes and return to the same pot.
Mash the potatoes. It is fine to leave them slightly lumpy, as you can mash further.
In a sauté pan, melt 8 tablespoon of the unsalted butter over medium heat before adding the garlic and sautéing until fragrant (30 seconds to 1 minute).
Reduce the heat to medium-low, and add the half-and-half to the sauté pan.
Mix the milk into the garlic butter gently using a whisk until fully combined. This is homemade heavy cream.
Add the homemade heavy cream to the mashed potatoes.
Gently stir the heavy cream into the mashed potatoes until fully incorporated.
Add the salt and pepper to the pot of potatoes.
Stir in the salt, pepper, and horseradish before transferring to a serving bowl.
Once transferred to a serving bowl, place cut pieces of 2 tbs of butter on top of the cooked, hot mashed potatoes
Garnish the buttered mashed potatoes with chopped chives.