2 1-inch-thick slices pork loin (6–8 ounces each)
1 1/2 cups dry white wine
2 onions, cut into 1/2-inch-thick slices
3 tablespoons olive oil, divided
Kosher salt and freshly ground black pepper
1 pound small (2-inch-diameter) Yukon Gold potatoes, cut into 1/2-inch-thick rounds
1/8 cup chopped fresh sage leaves
4 thin slices prosciutto
Asparagus spears, optional
Preheat oven to 450°. Pierce pork slices all over with the tip of a paring knife. Place in a dish just large enough to hold pork in a single layer. Pour wine over and let marinate at room temperature while preparing other ingredients.
Place onions in a medium bowl, drizzle with 1 Tbsp. oil, and season with salt and pepper. Toss gently to coat without breaking up slices. Transfer onions to prepared baking sheet, spreading out in an even layer. Combine remaining 2 Tbsp. oil, potatoes, and sage in same bowl; season with salt and pepper and toss to coat. Place potatoes on sheet, tucking in among onions.
Roast onion-potato mixture until potatoes are beginning to brown around the edges, about 20 minutes. Remove pork from wine and pat dry. Season with salt and pepper and top each pork slice with 2 prosciutto slices. Place pork on baking sheet atop potatoes and onions. Add asparagus spears if desired. Roast until an instant-read thermometer inserted horizontally into center of pork registers 135°, about 15 minutes. (After 10 minutes, I turned pork chops over to brown more evenly. I lifted the prosciutto , turned the chops and placed the prosciutto back on the chops.) Remove pan from oven and let rest, covered with foil for about 10 minutes. Serve.