Prepare the pork: Mix 2 tablespoons brown sugar, 2 teaspoons each mustard powder and chile powder, 1 tablespoon salt and 1/4 teaspoon pepper in a bowl. Put the pork on a plate, pat dry and rub all over with the spice mixture. Refrigerate, uncovered, at least 4 hours or overnight.
Whisk the remaining 2 teaspoons brown sugar, 1 teaspoon each mustard powder and chile powder, the Worcestershire sauce, vinegar, 1/4 teaspoon salt, and pepper to taste in a bowl; set aside for brushing.
Preheat the oven to 375 degrees F. Rinse the pork and pat dry. If desired, tie kitchen twine around the pork in a few places to help it keep its shape. Heat the olive oil in a large skillet over medium-high heat. Add the pork, fat-side down, and sear until golden, about 5 minutes. Continue to cook, turning, until golden all over, about 5 more minutes. Transfer to a rimmed baking sheet, fat-side up, and roast 30 minutes. Brush with three-quarters of the vinegar mixture; continue roasting until a thermometer inserted into the center registers 145 degrees F, 15 to 20 more minutes. Transfer to a cutting board and brush with the remaining vinegar mixture. Let rest 15 minutes before slicing.
Meanwhile, make the peas: Bring 6 cups water, the granulated sugar and 1/4 teaspoon salt to a boil in a saucepan. Add the peas, bring to a simmer and cook until tender, 8 to 10 minutes for fresh peas or 3 to 4 minutes for frozen. Drain, transfer to a bowl and keep warm. Add the cream to the pan, bring to a boil and cook until reduced by half, about 3 minutes. Whisk in the butter, then add to the peas and toss. Add the parsley and scallions, season with salt and pepper and toss. Serve with the pork.
Photograph by Con Poulos
Recipe courtesy Food Network Magazine