Sugarless Chocolate Fudge

16 ounces cream cheese softened
2 (1 ounce) squares unsweetened chocolate, melted and cooled
24 packages aspartame sweetener (equivalent to 1/2 cup sugar)
1 teaspoon vanilla extract
1/2 cup chopped pecans

Beat cream cheese, chocolate, sweetener and vanilla extract until smooth. Stir in pecans. Pour into an 8-inch square baking pan lined with foil. Cover and refrigerate overnight.