In a large saucepan, melt butter with sugar, heavy cream and a pinch of salt. Cook and stir over medium heat until mixture begins to boil. Boil for 5 minutes, stirring continuously. Remove from heat.
In a large bowl (for a stand mixer), add white chocolate morsels, marshmallow crème and lemon zest. Pour hot butter mixture over morsels and using the whisk attachment, beat until smooth (and chocolate has melted, about 1-2 minutes). Gently mix in lemon curd and mini marshmallows.
Pour fudge into a 9-inch square baking dish lined with parchment paper. Chill in refrigerator for one hour. Top fudge with lemon curd and graham crackers. Chill for an additional 3 hours, until fudge has set completely.
Cut into bite sized pieces and store in a covered container in the refrigerator. Serve cold and ENJOY!