Line a 9x13 bake dish with parchment paper.
Combine all of the ingredients (except the walnuts) in a large pot and place over medium heat.
12 ounces white chocolate baking chips, 2/3 cup evaporated milk, 1 cup granulated sugar, 1/2 cup dark brown sugar, 12 tbsp salted butter, 2 tsp vanilla extract, 1/2 cup mashed sweet potatoes, 1 tsp ground cinnamon, 1/4 tsp ground ginger
Let the ingredients melt, stirring continuously.
Once the mixture is nice and smooth, turn the heat up to medium high.
Stir, and let the candy mixture get up to 240 F. Use a candy thermometer for accuracy.
Remove the fudge mixture from the stovetop, add it the walnuts, and stir.
1/2 cup chopped walnuts
Pour the mixture into the parchment paper-lined bake dish and let cool.
Once completely cool, cut the fudge into desired shapes.
Enjoy!