Cut 1 pork tenderloin in half lengthwise, cutting to, but not through, other side; open halves, laying the pork flat.
Cut each half lengthwise, cutting to, but not through, other side; open halves, laying pork flat. Repeat the procedure with remaining tenderloin.
Sprinkle inside of tenderloins with 1 tablespoon parsley, 1/2 teaspoon salt, black pepper, and minced garlic. Top each tenderloin with 6 dried plums and 2 tablespoons piquillo peppers.
Roll up each pork tenderloin, jelly-roll fashion, starting at long side. Secure pork at 2-inch intervals with twine; dust with flour.
Heat oil in a large ovenproof nonstick skillet over medium-high heat.
Add pork; cook 6 minutes on each side or until browned.
Add the remaining 1 tablespoon of parsley, onion, peppercorns, unpeeled garlic, and bay leaf; saut 2 minutes. Stir in broth, sherry, and cumin. Wrap the handle of pan with foil, and transfer pan to oven. Cover and bake at 400 for 25 minutes or until a thermometer registers 160 (slightly pink).
Transfer pork to a platter; let stand 5 minutes.
Cut pork into 3/4-inch-thick slices, and sprinkle with remaining 1/4 teaspoon salt.
Remove whole garlic cloves; squeeze to extract pulp. Stir into pan juices (discard garlic skins and bay leaf).