Line an 8” X 8” pan with parchment on the bottom and sides and grease the parchment.
In a medium saucepot, whisk sugar and water together then heat over medium high heat, whisking continuously, until mixture comes to a boil. Insert candy thermometer and boil, undisturbed, for about 5 minutes or until temperature reads 240˚F.
Pour in cream and boil for 5 minute or until temperature comes back up to 240 F. Caution: Adjust temperature down, if mixture bubbles to the top of the pot then adjust temperature back up, when possible.
Remove pot from heat and stir in the butter, white chocolate, and vanilla until chocolate is melted.
Cool mixture for 10 minutes or to about 140 F. then beat fudge for up to 5 minutes until thickened. The fudge will be less shiny when ready.
Fold in cranberries and walnuts then quickly pour fudge into prepared pan while still warm. Let fudge come to room temperature. Cover tightly until ready to cut and serve.