Slow-Roasted Pork Leg Cochon-de-Lait Style

1 (18-20 lb.) pork leg (Boston & Picnic cuts attached, deboned and trussed)* ½ c. kosher salt ¼ c. paprika ¼ c. garlic powder 3 T. cayenne pepper 1 T. black pepper 2 c. white wine ½ c. unsalted butter,…