I think it's sometimes difficult to improve on perfection, such as a good Bordeaux. However, raspberries, Cognac? I serve this with Apple pie, ice cream or cheese for dessert. It isn't too sweet that it over powers but compliments Instead.
Using a non aluminum four quart pot, combine raspberries, sugar and wine. Bring to a boil on medium high heat, stirring about once every thirty seconds. Remove from heat when boiling begins. Cool to room temperature, pour mixture into a bowl, cover with plastic wrap. Place bowl on the counter, or somewhere out of the way, not the refrigerator, for 24 hours.
Strain through a fine sieve or cheesecloth into a clean bowl.
Add the Cognac and stir lightly. You may pour this into a bottle or pitcher. It will keep well for a month if covered and refrigerated.
It is now ready for drinking. You know you want to... Go ahead and taste it... Go on.