Spray a 6 - 7 quart slow cooker with non-stick spray. Place potatoes in slow cooker then pour water evenly over top.: The air will smell faintly of starch as you arrange the pieces, and that first pour of water will bead on the hot insert if you preheated it, otherwise it will settle into the crevices between the chunks. This tiny pool of moisture is crucial to creating steam, which cooks the potatoes evenly without drying them out. You should hear a quiet hiss if the cooker is warm, and see the pieces glisten under the light. Why it matters: even contact with a bit of water prevents sticking and promotes uniform tenderness. Troubleshooting: avoid crowding the pot so the steam circulates, and resist adding a large volume of liquid which would dilute flavor.
Toss with salt and pepper then add garlic and pour butter evenly over potatoes and garlic. Cover and cook on high heat 4 - 4 1/2 hours until potatoes are tender when pierced with a fork (don't drain!).: As the heat rises, the scent of garlic will soften and become fragrant, blending with melting butter . The slow, steady heat coaxing the aromatics into the potatoes creates a sweetness you will notice when lifting the lid. Visual cues include steam rising and a gentle simmer just at the edges on some models. Why it matters: cooking the garlic with the potatoes allows the flavor to integrate rather than sit on top. Troubleshooting: do not remove excess cooking liquid; it helps keep the mash creamy. Common mistake: lifting the lid frequently extends cook time and cools the pot.
Mash potatoes with a potato masher then add sour cream, heavy cream.: When you press down with the masher you will feel the potatoes give way, and the texture transforms from chunk to billowy mass. The first smells will be rich, buttery, and rounded from the cooked garlic . Adding cold dairy will slow the heat so warm the cream first, but if you add it here you are introducing tang and fat that cling to starch for a luscious mouthfeel. Why it matters: mashing by hand preserves a bit of texture and prevents a gluey paste which can happen with over processing. Troubleshooting: if potatoes feel gluey, stop mashing and switch to a gentler fold to combine.
Whip with an electric hand mixer until desired texture is reached, while adding in milk to reach desired consistency.: The mixer will hum and the mixture will become glossy, with small peaks and swirls that settle into a creamy blanket. As you drizzle in warmed milk , pay attention to the sound and look; the mix should smooth without becoming soupy. Why it matters: whipping aerates the mash for a lighter result than ramming it exclusively with a masher, and milk is your control knob for looseness. Troubleshooting: use short bursts with the mixer to avoid over aeration which can make the mash gummy; if that happens, fold by hand instead.
Serve warm with more butter if desired and minced chives.: The final presentation should glisten with melted butter and smell faintly sweet from the cooked garlic . Garnishing with minced chives adds color and a fresh bite that contrasts the rich mouthfeel. Why it matters: finishing butter and chives elevate the plating and add layered flavors that guests notice first. Troubleshooting: do not over salt at the end; taste before adding more, because the finishing butter can alter perceived seasoning.