Place white chocolate chips, brown sugar, molasses, evaporated milk, and all spices in a medium saucepan. Stir to combine, then place over medium-low heat. Stir almost continuously until melted and smooth. Pour into prepared pan. Top with sprinkles, if desired.
Gift suggestion: Buy cookie cutters in desired shapes. Line the bottoms with two laters of foil so the bottom is sealed, almost like a cookie-cutter shaped pan. Pour fudge into cookie cutters and decorate with sprinkles. Let set, then wrap in cellophane and give as gifts!