In a small bowl, mix all ingredients for the crust until completely moistened. Divide evenly between 4 individual tart pans and press in. Place into the freezer while you make the filling.
For the filling, stir sugar and salt into cream in the top of a double boiler. {A heat-proof bowl over lightly simmering water works just fine!} Stir occasionally to heat cream thoroughly and dissolve sugar, about 7 minutes or so.
Temper egg yolks with hot cream and mix. Pour that mixture into the double boiler and stir frequently for 10-12 minutes so the mixture can thicken.
Remove from heat and stir in chocolate chips and vanilla extract. Stir until chocolate has melted and filling is a smooth and uniform consistency.
Pour into tart shells evenly and sit out at room temperature. {Because the shells were in the freezer, this should take 30 minutes or so.} Place plastic wrap directly onto the filling of the tarts and refrigerate at least 2 hours or until the filling has set. {You should be able to remove the plastic wrap cleanly--with no filling on it.} Store in refrigerator until ready to serve.
When ready to serve, remove tarts from fridge. Top with 1/2 cup mini marshmallows each and torch the top to toast. {Or stick them under a hot broiler for a few seconds.} Serve immediately.