In a medium saucepan mix together red wine and sugar. Bring the red wine and sugar to a boil over medium heat stirring occasionally. Reduce heat to a low simmer and add ½ of the blackberries and ½ of the raspberries. Set aside the remaining berries for later.
Allow the sauce to simmer for approximately 30 minutes. Midway through the simmering time, use a potato masher to crush the berries in the sauce.
Skim the foam as needed as sauce simmers.
The sauce is ready, when it is slightly thickened and coats the back of a spoon.
Remove the sauce from the heat and allow it to cool to room temperature. Transfer it to a glass bowl or container and refrigerate it until you are close serving time.
Remove it from the refrigerator and add the remaining berries. Stir very gently to combine and allow the sauce to come to room temperature before serving.
This sauce will keep in the refrigerator for 1 week.
My Top Tips♥ Use a Good Red Wine - Please do not use a "cooking wine". Use a wine that you enjoy drinking for this recipe. A fruit forward red wine such as Malbec, Merlot, Bordeaux Blends, and Claret are excellent choices.♥ Get the Very Best Flavor& Visual Appeal - If you do not need to use all of the sauce at once, portion out the amount of sauce you need and add fresh berries to that portion.♥ This Sauce is More than an Ice Cream Topping! - You can also serve this berry dessert sauce over cakes like pound cake, coconut cake, angel food cake, puddings like white chocolate and vanilla, and also over plain cheesecake and baked brie cheeseSubstitutions♥ Use Frozen Berries - If fresh berries are not available, use frozen. Add the frozen berries to the wine and sugar as it comes to a simmer. Then use more thawed frozen berries in the final step to have the fresh, whole berry look and taste.♥ Use Different Berries - Boysenberries, marionberries, and blueberries all will make a delicious sauce too.