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1
Make the onion spread: Heat the vegetable oil in a large skillet over medium-low heat.
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2
Add the onion and a pinch of salt; cover and cook, stirring, until golden, about 35 minutes.
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3
Add the shallots and scallion whites; cover and cook, stirring, until browned, about 25 more minutes.
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4
Stir in the scallion greens, then remove from the heat and let cool.
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5
Chop the onion mixture and transfer to a bowl.
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6
Add the sour cream, mayonnaise, vinegar, Worcestershire sauce and 1 teaspoon salt.
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7
Cover and refrigerate at least 2 hours and up to 1 day.
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8
Make the beef for the sandwiches: Mince the garlic, then sprinkle with 1 teaspoon salt and mash into a paste with the flat side of a large knife.
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9
Transfer to a bowl; add the olive oil, celery salt, cayenne and 1/2 teaspoon black pepper.
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10
Cut small slits all over the beef with a knife, then use your fingers to push the garlic paste into the slits.
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11
Cover; refrigerate at least 1 hour or overnight.
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12
Preheat the oven to 425 degrees F. Bring the beef to room temperature.
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13
Sprinkle with 2 teaspoons salt and 1/2 teaspoon pepper.
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14
Place on a rack in a roasting pan; add 1 cup broth, 3/4 cup water, the celery, onion and parsley to the pan.
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15
Roast 10 minutes, then reduce the oven temperature to 350 degrees F and roast until a thermometer inserted into the center of the beef registers 115 degrees F, about 45 more minutes.
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16
Transfer to a cutting board; let rest 20 minutes.
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17
Strain the pan juices; reserve.
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18
Meanwhile, make the jus: Melt the butter in a medium saucepan over medium heat.
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19
Add the flour and cook, stirring, 1 minute.
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20
Whisk in the reserved pan juices and the remaining 3 cups broth and bring to a boil, whisking.
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21
Remove the pan from the heat and stir in the sherry.
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22
Brush the rolls with some of the onion spread.
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23
Thinly slice the beef against the grain.
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24
Dunk the slices in the jus, then layer on the rolls.
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25
Serve the remaining jus in small bowls for dipping.
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26
Photograph by Jonny Valiant
