Prepare pan: Line an 8x8-inch baking pan with parchment paper. Lightly butter edges so fudge comes out easily.
Melt chocolate: In a medium saucepan, combine white chocolate chips, sweetened condensed milk, and butter. Heat on low, stirring constantly until smooth.
Add flavor: Remove from heat. Stir in champagne, vanilla extract, and a pinch of salt. Mix gently until combined.
Pour and smooth: Pour mixture into the prepared pan. Spread evenly with a spatula. Sprinkle optional toppings if desired.
Chill: Refrigerate at least 2 hours or until firm. Cut into squares and serve.