Line a baking sheet with foil. In a small heatproof bowl, set over hot (not simmering) water, melt the semisweet chocolate with 1 teaspoon of oil.
In another small heatproof bowl set over hot water (not simmering), melt the white chocolate with the remaining 1 teaspoon of oil. Leave both bowls over the hot water.
Pick up one piece of fruit at a time and dip it into the melted dark or white chocolate, coating about half of each piece of fruit. If desired, drizzle the dipped portion with a contrasting color of chocolate and sprinkle with some chopped nuts.
Place the fruit on the foil lined baking sheet. Work quickly to coat the remaining fruit. Refrigerate for 5 minutes or until the chocolate is set. Keep in a cool place until ready to serve. (Fresh fruit should not be held for more than 4 hours before serving).