In a large bowl whisk together the flour, sugar, and salt. In a separate bowl whisk together the egg yolk, vanilla, and ice water. Cut the butter into the mixture with a pastry blender until pea-size clumps form. Slowly pour into the flour mixture, mixing until combined.
Knead the dough into a ball, and then pat flat and wrap with plastic wrap. Refrigerate for 1 hour.
After the dough has chilled, roll it out into a circle approximately ⅛-inch thick. Place into a 9-inch tart pan with a removable bottom. Trim the dough so that it is flush with the rim. Freeze shell for about 15 minutes so the dough can firm up.
Place a piece of aluminum foil on top and pour in pie weights or place a smaller baking dish on top of the foil. Place tart in the oven and bake at 350°F for 15 minutes.
Remove the weights and foil then bake uncovered for another 12-15 minutes until light golden brown. If the bottom of the crust puffs up, poke a few holes in it and carefully press down on the crust to remove the steam. Allow tart crust to cool in the pan while preparing the filling.
Salted Caramel Sauce
Heat sugar and water in a saucepan over medium-low heat, until the sugar is dissolved. If needed, use a wet pastry brush to wash down any sugar crystals on the side of the pan.
Increase the heat and bring to a boil without stirring, about 5 to 6 minutes, until the syrup is a dark amber color.
Remove the sugar from the heat and carefully whisk in the heavy cream. The mixture will bubble. Stir in the unsalted butter and salt. Set the caramel sauce aside, allowing it to cool at room temperature.
Add chocolate chips to a large bowl. In a small saucepan, bring the cream to a simmer over medium-high. Immediately pour cream over the chocolate and let it stand 1 minute. Stir gently until chocolate melts and the mixture is completely smooth.
Pour the chocolate into the cooled tart shell and refrigerate until set, 30 minutes.
Drizzle the surface of the tart with caramel sauce, top with chopped peanuts and drizzle with more sauce.
The sauce can be made up to a week ahead of time, stored in an airtight container in the refrigerator and re-warmed before adding to the tart. You will have a lot of extra caramel to enjoy after devouring the tart.