Place the chocolate chips, white chocolate, sweetened condensed milk, Irish Cream liquor, and vanilla extract in a large saucepan over medium low heat. Stir constantly until chocolate has melted.
Pour the fudge into a tin foil lined 8 x 8 dish.
Smooth the top of the fudge with a spatula and sprinkle with fleur de sel. Refrigerate for 1 hour, or until fudge is firm.
Cut the fudge into 40 equal pieces. Store in an airtight container in the refrigerator up to 4 weeks.