Pre-heat oven at 350 degrees.
For the crust - Take your crumbled cookies, melted butter and sugar and mix together. Press into your tart pan with the back of a measuring cup (or similar) to get a nice flat surface, also press crumb mixture up the sides as well. Bake at 350 degrees for 17-20 minutes. Let cool.
For the Ganache - Put chocolate in heat proof bowl. Heat heavy cream, when just about to boil remove from heat and pour over chocolate, let sit 5 minutes. Then gently stir in circular motions until cream and chocolate are completely blended and smooth. Pour over cooled crust. Let cool completely by putting in fridge or cool room.
For Dulce De Leche - Simmer can of sweetened condensed milk in water, covering the can, for 4 hours. You may have to add water over time. Let cool completely. Spread over ganache using offset spatula. (Note: you can buy prepared in the can, it is usually in same area as sweetened condensed milk at the grocery store.)
For the Whipped Cream - Using whisk attachment beat heavy cream until whipped cream is formed. Keep refrigerated and add right before serving. (If not sweet enough add 1 tsp sugar prior before whipping.)
For the Brittle - prepare cookie sheet by spraying with oil. Heat sugar and light corn syrup, stirring regularly, until golden brown, remove from heat immediately, stir in cashews and pour on prepared tray. Let cool. Break into pieces and arrange on tart.