Philadelphia Roast Pork Sandwiches

Cook fennel seeds in a small skillet over medium, stirring often, until toasted and fragrant, about 2 minutes. Transfer to a small bowl; let stand until completely cooled, about 5 minutes.

Place cooled fennel seeds in a spice grinder; grind into a powder, about 15 seconds. Return to small bowl; stir in sugar, rosemary, thyme, 2 tablespoons of the oil, 1 1/2 tablespoons of the salt, and 1/2 teaspoon of the crushed red pepper. Rub mixture evenly over pork to completely coat. Place pork on a wire rack set inside a large rimmed baking sheet lined with aluminum foil. Let stand at room temperature for 1 hour. Meanwhile, preheat oven to 450°F.

Roast pork in preheated oven until browned on top, about 20 minutes. Without opening oven, reduce oven temperature to 300°F. Continue roasting until a thermometer inserted into thickest portion of meat registers 165°F, 1 hour, 45 minutes to 2 hours. Remove from oven. Transfer pork to a cutting board set inside a rimmed baking sheet to catch juices. Loosely cover pork with aluminum foil; let rest at room temperature 30 minutes. Slice pork as thinly as possible. Transfer to a medium bowl, along with any carving juices. Add 1/4 teaspoon of the salt, and toss to combine.

While pork rests, stir together mayonnaise, chopped pepperoncini with brine, and grated garlic in a small bowl. Set aside until ready to use.

After about 20 minutes of pork resting time, heat sliced garlic and remaining 1/3 cup oil in a large Dutch oven or a deep, large skillet over medium, stirring often, until garlic turns light golden, about 5 minutes. Add broccoli rabe and remaining 1/2 teaspoon crushed red pepper. Increase heat to medium-high; cook, stirring often, until broccoli rabe stems are tender-crisp, about 4 minutes. Remove from heat; stir in lemon juice and remaining 3/4 teaspoon salt. 

Preheat oven to broil with rack about 10 inches from heat. Arrange rolls, cut side up, on a large rimmed baking sheet. Place 2 provolone slices on each bottom roll. Broil in preheated oven until cheese is melted, 1 to 2 minutes. Remove from oven. Divide pork evenly among bottom rolls. Top each with 1/3 cup broccoli rabe mixture. Spread 2 1/2 tablespoons mayonnaise mixture onto each top bun half. Cover sandwiches with top buns. Serve.