Set sous vide machine to 90C/194F.
Place peeled and sliced potatoes in sous vide bag (2 if necessary) with butter and smashed garlic. Remove the air through a vacuum sealer or the displacement method. Drop the bag in the bath for an hour and a half.
Remove bag from bath. Pour the butter and potatoes from the bag into a large mixing bowl.
Using a potato masher, mash the butter and potatoes. Once the potatoes are smooth, gently whisk in the sour cream, Lawry's seasoning salt (or salt) and pepper until mashed potatoes are creamy. Garnish with chives and enjoy!