In a small saucepan over lowest heat, slowly melt the chocolate and butter together over low heat. Remove from heat and stir in the marshmallows to melt and then the cream and vanilla. Refrigerate while making strawberry filling.
For the Strawberry Filling, crush or mash the first amount of strawberries. Combine the sugar and cornstarch in a small bowl and whisk. In a medium saucepan, heat the crushed berries with sugar until they start to get a little liquidy. Cook and then add the cornstarch mixture until lightly bubbling and thickening. Remove from heat and stir in extract and vinegar. Cool 15 minutes and then fold in fresh strawberries. Refrigerate 2 hours.
To assemble pie, spoon chocolate filling into pie shell. If the filling is too thick and cold, put it in a food processor and whiz with some whipping cream drizzled in, until it is soft enough to use as filling (but not gloppy). Top with the strawberry filling and then offer with dollops of sweetened whipped cream. Dust top with chocolate crumbs and diced strawberries. Serve at once or chill up to two days.