Spread the olives out on paper towels and leave overnight in a warm place to dry. Steep the olives in 2 parts olive oil to 1 part vinegar, seasoning with garlic, mint, peppercorns and salt, to taste. Cover, stirring occasionally, for 3 days. Transfer to sterilised glass jars and cover with olive oil. Refrigerate for up to 6 weeks. Serve the olives at room temperature.