Combine white chocolate, sweetened condensed milk, butter and vanilla in your Crock-Pot® slow cooker on high heat for 7-10 minutes, until melted.
Stir, and replace lid for 15 minutes longer, waiting until first "crust" forms across the top of the liquid. Stir again, replace lid, and wait 15 minutes more until second crust forms.
Stir until smooth and pour into small greased or parchment lined baking dish or loaf pan.
Note: if you grease, allow it to sit 5 minutes before cutting and serving for easy removal.
Optional: add sprinkles or top with them.
Notes
The ideal temperature for fudge is generally between 237 to 239 °F. For this fudge, the "skimming" process allows you to know when it's hot enough to pour, though!
How to Store
At Room Temperature - store in an airtight container for up to four weeks.
Refrigerate - You can refrigerate your white chocolate fudge for up to two months. Wrap it airtight because it can dry out faster in the cold air.
Freeze - Cut into slices and wrap with aluminum foil to keep it airtight before bagging. Freeze for up to six months.