325o 12 minutes

4 oz Bittersweet chocolate, chopped fine

½ cup heavy cream

¼ cup light corn syrup

8 whole graham crackers, crushed into crumbs (1cup), 

8 whole graham crackers, quartered along dotted seams

4 Tbsp butter, melted

1 Tbsp sugar

1 cup marshmallow crème

1-1/2 quarts chocolate ice cream, softened

22-26 large marshmallows, halved crosswise
Springform pan

Parchment paper
In medium microwave bowl, combine chocolate, cream and corn syrup and microwave until melted and smooth, about 1 minute, stirring halfway through.  Cool to room temperature, about 30 minutes.

Adjust oven rack to middle position.  Spray 9” springform pan with PAM and line sides with 2-1/2” wide strip of parchment paper.  Combine graham cracker crumbs, butter, and sugar in bowl until mixture resembles wet sand.  Using bottom of measuring cup, press crumbs into even layer on prepared pan bottom.  Bake until fragrant and beginning to brown, about 12 minutes.  Cool completely.

Pour cooled chocolate mixture over crust and smooth into even layer; freeze until firm, about 30 minutes.  

Spread marshmallow crème over fudge in even layer; freeze until firm, about 15 minutes. 

Spread ice cream evenly over marshmallow layer. Cover with plastic wrap; freeze until very firm, at least 4 hours.

Adjust oven rack 6 inches from broiler element and heat broiler.  Place cake on baking sheet; discard plastic; arrange marshmallow halves, cut side down, in snug layer over top.  Broil until marshmallows are lightly browned, 30 to 60 seconds rotating cake halfway through, (Refreeze cake if necessary).  

Working quickly, remove pan ring and parchment and place graham cracker quarters vertically along sides of cake and serve.