1. Preheat your oven to 350°F (180°C).
2. In a bowl of a food processor, process together pecans, sugar and flour until nuts are finely ground. Pour in butter; process until thoroughly moistened. Pat nut mixture onto the bottom and sides of a 10-inch (25 cm) fluted round tart tin with removable bottom. Bake for 15 to 20 min or until the crust is lightly colored. Cool on rack.
1. Place white and dark chocolate in separate bowls. Bring cream to a boil in a saucepan set over medium-high heat. Pour 2/3 cup (150 mL) of hot cream over white chocolate; pour the remaining cream over dark chocolate. Whisk white chocolate mixture until smooth and chocolate are melted. Repeat with dark chocolate. Let each cool for 10 min.
2. Pour the dark chocolate over the cooled crust, spreading evenly. Pour white chocolate over dark chocolate, tilting the pan to distribute evenly.
1. Drizzle caramel sauce over white chocolate in a decorative pattern. Refrigerate for at least 8 hours. Store in the refrigerator.