Get Ready: First, line a 9x13 inch baking dish with foil, then lightly mist it with cooking spray. Set it aside for later!
Combine & Heat: Grab a heavy 2-quart saucepan and toss in your granulated sugar, sour cream, butter, and salt. Stir everything together over medium heat until it starts to boil. Keep stirring often!
Reach Soft Ball Stage: Continue cooking the mixture, stirring now and then, until it hits the "soft ball stage" at 238°F. A candy thermometer is your best friend here for perfect results!
Melt Chocolate: Take the pan off the heat and quickly stir in your white chocolate chips until they're completely melted and smooth. This might take a few minutes.
Add Sweetness & Flavor: Next, add the marshmallow creme and vanilla extract. Stir gently until everything is perfectly smooth and blended.
Fold in Cranberries: Gently fold in the dried cranberries until they're evenly mixed throughout the creamy fudge.
Pour & Smooth: Pour the delicious fudge into your prepared baking dish. If needed, use an offset spatula to spread it out smoothly.
Cool & Chill: Let the fudge cool down to room temperature, then pop it into the refrigerator for several hours. This chilling time is key for firm, easy-to-cut squares. Slice and enjoy your delightful treat!