Grilled stuffed pork tenderloin

2 pork tenderloins (about 1 1/2 lb / 750 gr each)
2 teaspoons (10 ml) butter
2 tablespoons (25 ml) chopped onion
1 small clove garlic, chopped
1 tablespoons (15 ml) pine nuts
3/4 cup (175 ml) chopped mushrooms
1/2 cup (125 ml) fresh bread crumbs
1 tablespoons (15 ml) chopped fresh parsley
1 tablespoon (15 ml) chopped fresh sage
salt and pepper
2 tablespoons (25 ml) olive oil
2 tablespoons (25 ml) apple cider or apple juice

1. Butterfly pork tenderloins by splitting each horizontally in half, leaving 1/4 inch (5 mm) intact along other long side. Open like a book and pound to flatten slightly. Set aside.
2. In skillet, melt butter over medium-high heat; saute onion, garlic and pine nuts for about 2 minutes or until onion is softened. Add mushrooms; cook for 3 to 5 minutes or until softened.
3. Transfer to bowl and add bread crumbs, parsley and sage. Season with salt and pepper to taste; mix well. Spread stuffing over tenderloins, leaving border all around. Fold each half lengthwise and secure with greased skewers.
4. In small bowl, whisk together oil and apple cider for basting. Cook tenderloins on greased grill over hot coals or on medium-high setting, turning and brushing occasionally with cider mixture, for 30 minutes or until pork is no longer pink inside.