Combine olive oil, lime zest, lime juice, garlic, mint, pepper, and salt in a shallow dish large enough to place the lamb chops in one layer. Coat both side of the chops in the marinade and leave for 2 hours at room temperature, or up to 24 hours refrigerated.
For the sauce, melt butter in a medium skillet over medium heat. Add onions and garlic and sauté for 8 to 10 minutes, or until golden. Season with salt and pepper.
Stir in wine and bring to a boil. Reduce heat and simmer for at least 1 hour, or until mixture thickens and reduces to approximately 1 cup. The glaze should be the consistency of syrup.
Grill the chops for 3 to 4 minutes on each side or until desired doneness.
To serve, allow 2 chops per person, with Shiraz reduction.