Molly Baz

 1. Boil the potatoes:
In a large pot, cover 5 lbs yukon gold potatoes with cold water. Season with a bigggg handful of salt. Bring to a simmer over medium high heat. Simmer until tender, 30-45 minutes (depending on the size of your potatoes). Drain.
Let cool until still quite warm, but easy enough to handle. (Skip down to step 4 for the step by step on how to peel and mash.)
2. Meanwhile, steep the milk:
Cut 2 garlic heads in half crosswise (no worries if they fall apart, they’ll ultimately get strained out.)
Combine 2 ½ cups milk, 5 tablespoons butter, 2 tablespoon salt, and the halved garlic in a medium saucepan. Bring to a simmer, remove from the heat, cover and let steep while the potatoes finish cooking.
3. Finish your prep:
Thinly slice 1 bunch of scallions (white and green parts) and 2 bunches of chives. Set a big handful of each aside for serving.
In a medium bowl, whip ½ cup heavy cream to stiff peaks. Keep cold until ready to serve.
4. Mash:
Once the potatoes are no longer piping hot. If you want to peel them, hold a kitchen towel in one hand and a paring knife in the other. Use the knife to peel away and discard the skins. Return the peeled potatoes to their pot. (You can also use a ricer at this point, to rice and remove the skins right into the pot, or you can embrace the rustic vibe of a potato skin and leave the skin on.)
Using a potato masher, mash the potatoes until relatively well mashed and homogenous. There will still be some little chunks, this is the nature of a rustic mash.
Strain the hot milk/butter mixture over the mashed potatoes and whisk gently to incorporate it well. As you mix it will turn from liquid-y to thick.
Stir in ½ cup sour cream, and the sliced scallions and chives.
5. Serve:
To serve, classic, and as is: Just before serving, use a spatula to fold in the whipped cream. Taste and add more salt if needed (chances are they will.) potatoes to a serving bowl and top with the reserved chives and scallions, and freshly ground black pepper.
To make ‘em ahead: Transfer the potatoes to a 9 x 13 baking dish and let them cool to room temperature.. Coarsely grate 4 ounces sharp cheddar, if using. Fold the cheddar into the reserved whipped cream. Spread the whipped cream over top of the potatoes. When ready to serve, preheat the oven to 400. Bake the potatoes until browned on the top. Sprinkle with the reserved chives and scallions and serve hot.