Porchetta
Thaw porchetta completely in the refrigerator.
Preheat oven to 500 degrees F.
Place porchetta on a wire rack in a rimmed baking sheet.
Sear until golden brown, about 20-30 minutes. Turn occasionally to ensure an even sear.
Reduce heat to 350 degrees F and continue roasting. Rotate the pan and turn porchetta occasionally, until an instant read thermometer inserted into the center of the roast reads 140 degrees F. about 1.5 to 2 hours.
Remove from oven and allow to rest 30 minutes.
Slice and serve with pickled vegetables.
Pickled Vegetables
While the Porchetta cooks make the pickled vegetables. Combine the vinegar, sugar, salt, and pepper in a saucepan, stirring until the sugar dissolves, and bring to a boil, over high heat; cook 2 minutes. Combine the vegetables in a bowl and pour the vinegar mixture over, let cook 15 minutes. Cover the bowl and refrigerate at least 1 hour.
Drain the vegetables and discard the garlic slices. Serve with sliced Porchetta.