This is very much like a salad my mother used to make. I have tried to make it like hers, but of course I have had to try different fruits. Everyone loves it. When I made it the first time for my mother in-law, she couldn't say enough good about it. She asked me to make it again the next week. Winner for that alone!
You can use any combination of your favorite or available fruits. I usually use a combination of fresh and canned fruits. This picture has strawberries, blueberries, grapes, apples and bananas that are fresh. I also added canned mandarin oranges, pineapple and papaya. (I sometimes add canned peaches and pears if I don't have enough fresh fruit.)
I like fresh as much as possible.
Drain the canned fruits and reserve the juice. Put 2 cups of the juice in a small pot and bring to a boil. (If you don't have 2 full cups, you can add some orange juice or water.) While it is coming to a boil, mix the cornstarch and sugar in a bowl until there are no cornstarch lumps.
Once the juice is boiling, add enough of the sugar mixture to thicken the juice. Let cook for a couple of minutes until it is thick. Remove from heat and let cool. I make sure it is cold, usually in the refrigerator for a couple of hours, you will find it to be the consistency of pudding.
Cut up fresh fruit into bite sized pieces and add to the canned fruit. Before you do this, you might want to make sure no more juice has gathered at the bottom of the bowl. If it has, discard before proceeding.
Mix the sour cream with the cooled, thickened juice/pudding. Add to the fruit a little at a time until it has the desired amount. Each of us is different and like different amounts of the dressing on salads. I like lots, but some don't. Eat and enjoy!
NOTE: I wouldn't add the bananas, if you are using them, until you are ready to serve.