Place cubed potatoes into a medium pan, cover with water and place on stove over medium high heat.
Boil until potatoes are fork tender, about 25 minutes.
Melt 1 tbsp butter in a skillet over medium heat, add diced onion and minced garlic.
Sauté until the onions are golden brown.
Drain potatoes once soft and add to a medium mixing bowl.
Mash potatoes until smooth, add the remaining 3 tbsp butter, and your sour cream. Stir to combine.
Fold the onions and grated cheese into the potato mixture until combined.
Refrigerate until ready to use!