Fudge that Doesn't Fail

We are big fudge lovers in this family. Its my husband that usually makes it using a recipe that his mother gave to him. The problem with that recipe is that it fails 50% of the time with no explanation. Instead of having beautiful chocolaty squares we will end up with a chocolate puddle.
This fudge recipe will never fail you. You will no longer have to worry about having a chocolate puddle.

Ingredients

1 1/2 cups of sugar
2 tbsp butter
1/2 tsp salt
1/2 cup evaporated milk
2 cups semisweet or bittersweet chocolate chips
2 tsp vanilla extract
3/4 cup walnuts in large pieces

Grease an 8-inch square baking pan with butter or vegetable shortening.

Combine sugar, butter, salt, and evaporated milk in a large sauce pan over medium heat. Stir constantly until mixture comes to a boil, then lower heat and stir in chocolate chips. Continue to stir gently until the chocolate melts and the mixture is smooth. Stir in the vanilla and walnuts.

Pour and scrape into prepared pan, cover and chill until firm, about 2 hours. Cut into squares to serve. Store in an air tight container at room temperature for up to a week.