Line a 9x9" or 8x8" pan with foil and spray with nonstick cooking spray.

Place white chocolate chips and sweetened condensed milk in a large microwave safe bowl. Heat for 1 minute on high power; stir. Heat an additional 30 seconds, stirring after, and continuing until mixture is just melted together and smooth.

Stir in vanilla and salt, then spread in prepared pan. Chill to set (sometimes it'll set on the counter, but it'll take longer and depend on the how warm your house is).

Slice into 1" squares. Store in an airtight container in the refrigerator for up to 2 weeks.

Cookies & Milk Fudge: add 1 cup each chopped Oreos and chocolate chips cookies (or 2 cups of your favorite cookie) in step 3. Sprinkle additional cookies on top for garnish, if desired.

Peanut Butter Fudge: add 1/2 cup peanut butter to the chips and sweetened condensed milk in step 2 (before heating). Melt as directed. The mixture will look a little bit seized after melting, but that's okay. Spread it in pan as directed. If desired, add 1 cup of chopped candy in step 3.

Mint Chip Fudge: add 2 teaspoons peppermint extract and 2-3 drops of green food coloring in step 3, then stir in 1 cup mini or regular sized chocolate chips. Spread in pan as directed.