Note: to prep these ahead of time, wash, peel and chop your potatoes. Place them in a large bowl and cover them with cold ice water. Store them in the fridge for 12 to 18 hours before preparing.
Slice the potatoes in half or in quarters, depending on the size. You want the potato chunks to all roughly be the same size.
Place the potatoes in a large pot of cold water over medium heat. Season the water with a big pinch of salt. Bring the potatoes to a boil, then boil until they are fork tender, about 12 to 15 minutes. (If your potato chunks are smaller, check after 10 minutes.)
While the potatoes are boiling, heat the butter and cream in a saucepan over medium-low heat until the mixture is warmed through.
Drain the potatoes well and place them back in the pot. Use a potato masher or ricer to begin mashing the potatoes into the consistency you enjoy. Mash in half of the butter and cream mixture and 1 teaspoon salt. Now is the time to use the hand mixer but you don’t want to over mix! Keep it on low speed and move it around the bowl constantly, just for a minute or two, breaking up any larger chunks that didn’t mash. Stir in the rest of the milk and butter mixture. Stir in the manchego and let it melt for a minute or two. As it sits in the potatoes, it will get warmer and meltier! Use the hand mixer a few times to blend everything together. Taste and season the potatoes with more salt if needed. This will depend on how salty your cheese is! Do not be afraid to add more salt if needed.
Once whipped and smooth, top with fresh chives. Serve the potatoes with a few pats of butter on top if you wish.
To serve 4: Cut this recipe in half exactly. Taste and season with more salt if necessary.