I first made this for a birthday as a topping of a chocolate peanut butter cake that I topped with peanut butter M&Ms (which was absolutely delicious, by the way.) You can find the full recipe here, but the cake, filling, and topping done their way took a lot of time. Here is just the topping, which they have called ganache, but I think it's more like a fudge sauce. I have made it since and used it to top box-cake, but I let it simmer for extra time and it turns out that it will get much harder! It was good on cake, but it would also work well on fruit, especially if you let it simmer for a couple of extra minutes. The last step is to let it chill, but I found that for cake it wasn't necessary, and wouldn't be for fruit either.
Fast & Lite Fudge Sauce
2/3 cup granulated sugar
1/3 cup evaporated fat-free milk
1 tablespoon butter
1/8 teaspoon salt
2 (1-ounce) squares bittersweet chocolate, chopped
1 teaspoon vanilla extract
Combine 2/3 cup granulated sugar and next 4 ingredients (through 2 ounces bittersweet chocolate) in a medium saucepan over medium heat; bring to a boil. Cook 2 minutes or until sugar dissolves and chocolate melts, stirring constantly. Remove from heat. Stir in 1 teaspoon vanilla; cool completely. Chill 30 minutes or until thick.