Preheat oven to 350 degrees Fahrenheit.

CRUST: In a food processor, pulse Oreos until fine crumbs. Add melted butter. Mix thoroughly. Press into the bottom and up the sides of an 8-inch tart shell. (May also use 9-inch pie dish.) Bake at 350˚F for 8 minutes. Remove and cool slightly.

CARAMEL: Melt butter with the brown sugar in a small saucepan over medium heat, stirring frequently with a spatula until the mixture begins to bubble. Continue cooking and stirring for 1 minute. Simultaneously nuke heavy cream for 30-60 seconds in microwave, until simmering. Remove caramel from the heat and stir in the warm heavy cream and vanilla. *Careful it will bubble up. Pour caramel into the prepared Oreo crust. Then place in freezer for about 30 minutes until chilled and set, but not frozen.

CHOCOLATE GANACHE: Place chocolate chips in a glass bowl. Bring heavy cream to a simmer in a saucepan or for 30-60 seconds in the microwave. Pour hot cream over the chocolate chips, let sit for 1 minute, then whisk until completely smooth.

Pour ganache over caramel, and smooth or swirl with an offset spatula. Allow chocolate to set at room temperature or freeze for 15-30 minutes. Sprinkle with salt (kosher, sea salt, or fleur de sel) before serving. Cut into thin slices -- about 14. Lightly cover tart with plastic wrap and store at room temperature.