Seperate cranberries to cull out bad ones. Rinse remaining cranberries and put in food proccessor. Proccess using short bursts and scraping side of bowl till cranberrries are finely chopped. Put in glass bowl and cover with 1/2 cup of granulated sugar. Cover bowl with plastic wrap and refrigerate overnight at least 8 hours.
After cranberries have been refrigerated they will soak up sugar. Add chopped pecans and grapes. Mix well with wooden spoon. Cover and put back in refrigerator.
In a large bowl add heavy whipping cream, remaining sugar and vanilla. Beat on high till stiff peaks form. Fold in cranberry mixture and marshmallows. Cover and refrigerate for 2 or more hours. Then serve as a side dish or dessert.
Great side for those who are finicky about cranberries. Kids love it.