Whisk egg yolk, cream and vanilla together in a small bowl and set aside.

In a food processor, blend flour, sugar and salt about 5 seconds.

Add butter cubes to the food processor and pulse until the mixture resembles cornmeal, about 15 seconds.

With the machine running, add egg mixture and continue to process until dough begins to form, about 12 seconds.

Wrap dough in plastic wrap and chill about 15 minutes.

Roll dough between two pieces of plastic wrap, to about 1/4" thick. Roll dough in the general shape of your pan. I used a long rectangle (14"x4"), but you could use a round tart pan instead.

Remove top layer of plastic wrap, then flip the dough over, into the pan, allowing it to hang over the sides. Ease dough into the pan by gently lifting edge of dough with one hand, while pressing the dough into the corners with the other hand. Leave any dough that is hanging over the edges in place for the moment. Gently press dough into the groves along the sides of the pan (adding bits of dough as needed), then roll a rolling pin over the top of the pan to trim off any excess dough.

Cover tart pan with plastic wrap and place in the freezer for 30 minutes. (Dough lined tart pan can be wrapped tightly in plastic wrap and frozen for up to 1 month)

After 30 minutes (or more), remove tart from freezer, remove plastic wrap, and carefully press a sheet of foil into the frozen tart shell, covering the edges. Top foil with pie weights, dry beans or dry rice to weigh down the foil.

Place prepared tart on a baking sheet and bake in a preheated 375*F oven for 30 minutes. After 30 minutes, carefully remove the pie weights and the foil and bake (uncovered) for an additional 5-10 minutes, until golden brown.

Set aside to cool.

Unwrap caramels and place in a bowl with heavy cream. Heat in the microwave for 3-5 minutes at 50% power, checking and stirring every minute or so. Once the caramels are melted, stir well and add salt. Stir, then set aside to cool a few minutes.

Pour caramel into the (mostly) cooled crust. Move entire tart to the fridge and chill about 10 minutes.

Prepare truffles by cutting them in half. They do not have to be perfect pieces, but if you break a few, you can simply add them to the ganache (when you add the chopped chocolate to the cream, as directed below).

Chop the chocolate into small pieces.

Heat the cream in a bowl in the microwave until very hot (but no need to boil). Add chopped chocolate and then let it sit about a minute (if you have a few broken truffle pieces, you may add them as well). After a minute, stir until the chocolate is fully melted and well combined.

Place bowl in the fridge and allow to thicken a bit. You want it to be just soft enough to pour, but thick enough that when you top it with the truffles they will stay in place (and not sink into the ganache). Check the fridge and stir ganache every 10 minutes or so until desired thickness is met. Pour chocolate on top of caramel layer, and spread as needed with an offset spatula.

Top ganache with cut truffles, then dust tart with cocoa powder.

Chill about 15 minutes, then serve at room temperature.