Set the Oreo mold on a flat surface or tray that fits easily in your refrigerator.
Melt the white chocolate wafers according to the package directions until smooth. Stir in green sprinkles, starting with 1 tablespoon and adding more a tablespoon at a time until you like the amount of color and texture.
Spoon the sprinkle chocolate into each mold cavity, filling about halfway. Press a mint Oreo gently into the center, then cover with more sprinkle chocolate until the mold is full.
Tap the mold lightly on the counter to release any air bubbles. Place in the refrigerator and chill for at least 30 minutes, or until completely set.
Carefully remove the chocolate-covered Oreos from the mold. Use a small dab of melted white chocolate to attach the shamrock decorations. Let set, then serve at room temperature.