Heat the olive oil in a large skillet. Add the Garlic and cook over moderate heat until softened. Add the Chard stems and Onion, season with salt and pepper and cook until the Onion softens, about 4 minutes. Stir in the raisins, vinegar, honey and half of the Mint. Cover and cook until the Chard is crisp-tender, about 1 minute longer. Transfer to a bowl and let cool, then mix in the remaining Mint. Serves 6.