All Wrapped Up

Our Test Kitchen's twist on an old-school favorite is fancy and foolproof

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Southern-Style Beef Wellington

ACTIVE 1 HOUR, 20 MIN. - TOTAL 3 HOURS, 30 MIN.

1 (21⁄2-lb.) center-cut beef tenderloin, trimmed

1 Tbsp., plus 1⁄2 tsp. kosher salt, divided

3 Tbsp. canola oil, divided

3 Tbsp. country-style Dijon mustard

1 yellow onion, chopped (about 11⁄4 cups)

16 cups loosely packed stemmed, chopped fresh mustard greens (from 3 [8-oz.] bunches)

4 garlic cloves, finely chopped (about 2 Tbsp.)

1 Tbsp. Worcestershire sauce

1⁄2 tsp. crushed red pepper

4 oz. prosciutto (8 slices)

1 (17.3-oz.) pkg. frozen puff pastry sheets (such as Pepperidge Farm), thawed

All-purpose flour, for work surface

1 large egg, beaten Flaky sea salt

SERVES 6 TO 8

1. Tie beef crosswise at 2-inch intervals with kitchen twine. Sprinkle with 1 tablespoon kosher salt. Place on a baking sheet; let stand at room temperature 30 minutes.

2. Heat 2 tablespoons oil in a 12-inch cast-iron skillet over medium-high. Pat tenderloin dry. Cook, turning occasionally, until browned on all sides, about 8 minutes. Return to baking sheet; let cool about 15 minutes. Remove and discard twine. Brush tenderloin with mustard. Chill, uncovered, 30 minutes to 3 hours.