How to Cook Roast Beef in Oven With Potatoes
A tender, juicy roast isn't hard to pull off. Neither are creamy, golden-brown potatoes. But merging the two into a holiday centerpiece? That's where things get tricky.
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Juicy, tender, beefy roast
We opt for a top loin roast (a great and cheaper alternative to prime rib). We salt the roast overnight and cook it low and slow.
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Creamy, beefy-tasting potatoes
We introduce beefy goodness into the potatoes three different times and in three different ways during cooking.
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Plenty of potatoes
Instead of roasting the potatoes and the beef in a roasting pan (limiting how many potatoes can fit), we place the roast over the potatoes on a perforated sheet of aluminum foil, which also allows its juices to drip down onto them.
Roasting beef with potatoes, a hallowed British tradition, sounds like it will produce the ideal holiday spread. While the meat cooks, the spuds sitting underneath or around it soak up the drippings and transform into a flavor-saturated side dish that impresses just as much as (if not more than) the roast itself. But as smart and serendipitous as that sounds, it's folklore. In my experience, cooking the meat and potatoes together rarely produces the best version of either one; in fact, it pits the two components against one another.
The problem is partly due to a lack of space. Most roasting pans can't accommodate a piece of meat large enough to feed a crowd plus enough potatoes to go alongside. So the options are to cram the potatoes into the pan, which causes them to steam, thwarting flavorful browning, or to include only enough to feed a few guests.
The more fundamental issue is that the two components require radically different cooking methods. Low-and-slow heat is the best way to ensure that a large roast cooks evenly and stays juicy, but it also makes for sparse drippings and, thus, bland potatoes. On the other hand, the only way to really brown and crisp potatoes in the oven is to crank the heat way up. But who's willing to risk overcooking a pricey roast for the sake of the spuds?
Finding a way to roast enough beef and potatoes for a crowd while allowing the roast to cook up juicy and tender (and release flavorful drippings to infuse and crisp the potatoes) would require real strategy.
Top Shop
I often default to prime rib for the holidays because of its well-marbled meat and fat cap, which crisps up into a thick crust, making it feel festive. But there are other good options, such as top loin roast. This is the cut that produces strip steaks (its alias is "strip roast"), so it, too, boasts well-marbled meat and a nice fat cap. Plus, it's boneless and uniform, which makes it easy to cook and slice (see "Strip Steak in Roast Form").
Strip Steak in Roast Form
I crosshatched the fat cap to help it render and crisp and then salted the meat overnight to ensure that it would be well seasoned and juicy. And for the moment, I cooked the meat and potatoes separately (I'd tackle the merger later). I seared the roast, top and bottom, in a large roasting pan and then transferred it to a 300-degree oven, where it cooked gently until it reached 115 degrees. That's about 10 degrees shy of medium-rare, but the temperature of the meat would climb as it rested.
Potatoes won't crisp in a crowded pan even if the heat is blasting, so I scrapped that goal in favor of an old-school French preparation called fondant potatoes that creates marvelously flavorful results without crisping. To make them, you halve and brown the spuds on the cut sides and then braise them in fat and stock. The potatoes absorb the flavorful liquid, turning so velvety that they practically dissolve in your mouth (hence their nickname: "melting potatoes"). Not worrying about crisping also meant that I could pack plenty into the pan.
Key Steps: Beefing Up the Flavor of Potatoes
I browned 5 pounds of peeled, halved Yukon Gold potatoes (their starchy yet creamy consistency seemed ideal) in the rendered fat left in the pan, flipped them, poured beef broth around them, and returned them to a 500-degree oven. Thirty minutes later, they were plump and extremely tender. I transferred them to a platter and strained and defatted the remaining broth, which would make a nice jus for serving.
They tasted beefy on the outside but bland within—no surprise since commercial broth contains no fat and only moderate beef flavor. But the roast had those qualities in spades. Time for that merger.
Get Scrappy
One unique feature of top loin roast is the sinewy strips of meat and fat that run along either side of the roast. They're often left behind on the plate, but I decided to use them. I cut them off and sliced them into 1-inch pieces to brown alongside the roast.
Trimmings from a strip roast are rendered as the roast browns. The rendered fat and fond will be used to brown Yukon Gold potatoes, giving them plenty of rich, beefy flavor.
The results were worth the minimal knife work: The trimmings gave up loads more fat and fond for the potatoes to soak up. (Starting the meat and trimmings in a cold pan maximized the amount of fat that was rendered, because the fat had time to melt thoroughly before the meat's exterior browned too much.) I even doubled their efficacy by simmering the browned scraps with the broth before using it to braise the potatoes, which amped up the broth's beefiness and the flavor of the spuds. Further doctoring the broth with garlic and herbs rounded it out; adding gelatin gave the reduced jus unctuous body.
Cooking the meat and potatoes together wasn't tricky once I had extracted all that flavor and fat from the trimmings. But it did require a strategic setup. After searing the meat and scraps, I laid the potatoes cut side down in the pan, keeping them in a single layer to ensure even cooking, and covered them with aluminum foil that I'd poked holes in. That created a "rack" on which I placed the roast; it also allowed juices to drip through to the potatoes and trapped steam that helped the potatoes cook through. When the roast hit 115 degrees, I set it aside to rest; gingerly flipped the potatoes; added my beef-enhanced, strained broth (it simmered while the roast cooked); and finished the potatoes in a 500-degree oven.
It was a success: juicy, tender meat and creamy potatoes that tasted truly beefy.
There's no need to wait for a crowd to serve our Beef Top Loin Roast with Potatoes. With a smaller piece of meat and a 12-inch skillet, you can make our downsized version of the recipe, which serves four to six.
Source: https://www.cooksillustrated.com/articles/1136-roast-beef-and-potatoes-for-company