Combine the first 3 ingredients in a large bowl; beat with a mixer at medium speed until smooth. Add the condensed milk, and beat until combined. Stir in the whipped topping. Divide the mixture evenly between shells; chill 8 hours or until set (pies will have a soft, fluffy texture). Cut into wedges, and drizzle with chocolate syrup.
Note: We loved this pie frozen--its texture is more like that of an ice-cream pie.