I peel and cube my potatoes into even, bite-sized chunks so they cook at the same pace. Place them in a large stockpot and cover with cold water by about an inch. Bring the pot to a boil, then reduce to a simmer and cook for 15 to 20 minutes until the potatoes slide easily off a fork.
Once they're tender, I drain the potatoes in a colander and let them sit for a minute or two. This short resting time lets excess steam escape, which keeps my mash from turning watery. I've learned that skipping this step is one of the easiest ways to end up with soupy potatoes.
I return the drained potatoes to the warm pot and start mashing right away while they're still hot. Using a masher or ricer, I work through the chunks until they're mostly smooth, with just a few soft lumps left if I like texture.
Next, I fold in the softened butter first, letting it melt into the hot potatoes before pouring in the warm milk a little at a time. I stir gently so the potatoes stay fluffy instead of turning dense or gummy.
Finally, I mix in the sour cream for that creamy tang, then season with salt to taste. I always taste as I go here, adding a pinch more salt until the flavor feels balanced and comforting.
I like to transfer the potatoes straight to a serving bowl while they're still warm, topped with an extra pat of butter melting on top. This is the moment my family usually starts hovering around the kitchen.