How to Make It
Set the roast on a baking sheet and rub it all over with the salt and pepper. Refrigerate, uncovered, for 1 day.
Preheat the oven to 400°. Heat a large cast-iron skillet. Cook the roast, fat side down, over moderately high heat until well browned, about 3 minutes. Continue cooking, turning, until the meat is browned all over, about 5 minutes. Turn the meat fat side up and roast for 40 to 45 minutes, until an instant-read thermometer inserted in the center registers 125° for medium rare. Transfer the roast to a cutting board and let rest for 15 minutes.
In a blender, combine all of the ingredients and puree until smooth. Strain into a medium bowl.
In a small saucepan, bring the milk and garlic just to a boil. Drain the garlic and pat the slices dry on paper towels. In a small saucepan, heat 1/2 inch of canola oil to 275°. Working in 2 batches, fry the garlic, stirring, until light golden, 1 to 2 minutes. Using a slotted spoon, transfer the garlic to paper towels to drain. Season with salt and let cool.
Spread the arugula on a platter. Thinly slice the roast and arrange on the arugula. Drizzle a little hot sauce and olive oil over the meat and garnish with the garlic chips and scallions. Season with salt and pepper and serve the remaining hot sauce at the table.