Avoid peeling hot potatoes
Use less butter and eliminate the need to laboriously beat it in a little at a time
In the early 1980s, Parisian chef Joël Robuchon turned mashed potatoes into an utterly sublime experience by employing two hallmarks of French cooking: tireless attention to detail and a whole lot of butter.
His method: Boil 2 pounds of whole unpeeled potatoes and then peel them while hot before passing them through a food mill. Next, incorporate a full pound of cold butter, 1 tablespoon at a time, by beating vigorously with a wooden spoon—a 10-minute, arm-numbing process. Finally, thin the puree with warm milk and pass it repeatedly through a tamis (a flat, drum-shaped ultrafine sieve). Robuchon’s painstaking efforts produced the ultimate example of pommes purée, ethereally smooth and laden with butter.
While I love Robuchon’s recipe, the scandalous fat content and the drudgery of sieving make it unrealistic for a home cook. But if I could streamline the process and cut back somewhat on the fat, it would be a dish I’d love to make for special occasions.
In France, the puree is made with ratte potatoes, medium-starch fingerlings. I used Yukon Golds, a close substitute. For my first go-round, I cut the amount of butter in half and poured in extra milk to compensate; I used a food mill, but I skipped the tamis.
Was the resulting puree as gloriously smooth as Robuchon’s? Perhaps not, but tasters still called it “pillow-soft,” so I happily gave up any thoughts of trying to jury-rig a tamis. That said, the potatoes did lack the richness of Robuchon’s version. Adding butter back a little at a time, I found that 2½ sticks elevated these spuds to pommes purée status: a rich, silky step above regular mashed potatoes.
Now that I had experienced beating cold butter into potatoes, I was eager to find a way around it. How about melting the butter? Sadly, with so much of it in the mix, the butter and potatoes didn’t fully integrate, so the puree was separated and greasy.
Setting that problem temporarily aside, I turned my attention to the literal pain of peeling hot potatoes. I compared a puree made with peeled and diced potatoes (rinsed to remove surface starch) to one made with whole, skin-on spuds. The latter required more than a cup of milk to achieve the proper silken consistency. However, the peeled, diced potatoes absorbed so much cooking water that they could accommodate only ½ cup of milk. The result? A weaker-tasting mash. This got me thinking: Since potatoes are so absorbent, why not peel them and cook them in liquid I’d actually want them to soak up (the milk and butter)? I gave it a try, reserving the buttery cooking milk and whisking it into the milled potatoes. The puree was velvety-smooth and tasted rich and buttery. What’s more, it was not at all separated or greasy. This was a double victory: no more beating in cold butter or peeling hot potatoes.
Why did simmering the potatoes directly in milk and butter result in a more cohesive puree than adding melted butter and milk to boiled potatoes? It all comes down to the potato starch, which is critical for helping fat emulsify with potatoes. When peeled potatoes are boiled in water, much of their starch is released and eventually poured down the drain. With too little gluey starch in the mix, the melted butter struggles to form a smooth emulsion with the wet spuds, resulting in a slick, greasy puree. When the potatoes are cooked directly in the milk and butter, none of the released starch gets lost, and it is thus available to help the butter emulsify with the water in the potatoes. (In Robuchon’s recipe, the whole, skin-on potatoes retain their starch during cooking; vigorous beating liberates the starch and helps stabilize the emulsion, while the generous amount of butter prevents the released starch from turning the puree gluey.)
In the end, my simplified recipe delivered a rich, silky-smooth mash while allowing me to wave au revoir to an exhausted arm.
Keys to Success
Avoid peeling hot potatoesBoiling potatoes in their jackets prevents them from becoming waterlogged during cooking in Robuchon’s method, but it means peeling piping-hot potatoes. Our solution was to skip cooking the potatoes in water and instead cook them in milk and butter, which we then incorporate into the puree.
Use less butter and eliminate the need to laboriously beat it in a little at a timeBeating cold butter into the puree takes considerable time and effort. We eliminate this step by cooking the potatoes directly in the butter (and milk). We also determined that reducing the amount of butter in the dish by about 40 percent still yielded an impressively rich, flavorful, and smooth puree.