Butter an 8x8x2 inch baking pan; set aside.
Butter the sides of a heavy 2 quart saucepan.
In the saucepan combine the sugar, sour cream, and butter or margarine.
Cook over medium-high heat to boiling, stirring constantly with a wooden spoon.
Clip a candy thermometer to the side of the pan.
Reduce heat to medium.
Continue cooking to 238° (soft ball stage), stirring occasionally.
Mixture should boil at a moderate, steady rate over entire surface.
Remove from heat.
Stir in confectioners' coating and vanilla, stirring till coating is melted.
Add walnuts; stir till smooth and creamy and mixture starts to thicken (about 3 minutes).
Pour into the prepared pan.
Score candy while warm into 1 inch pieces.
Cool till firm.
Cut into pieces.
Store tightly covered.