Make the crust: Place your butter in a glass bowl or other large microwaveable container- OR you can melt the butter on the stove in a small saucepan, if you prefer. 

When the butter is melted, whisk in the sugar and salt, then add the flours and whisk in thoroughly. The dough will have kind of a sandy, wet texture. 

Use a spatula to scrape the tart dough into your tart tin and press the dough evenly over the bottom. I cover my hand with a plastic sandwich baggie to do this. 

Prick the crust several times with a fork and place it in the refrigerator to chill for 20-30 minutes before baking.

​Preheat the oven to 350 degrees. 

When ready, place the tart pan on a baking sheet, then in the oven to bake for 22-25 minutes, until golden brown.

While the crust is baking, prepare the filling.

Roughly chop your chocolate bars, if not done yet.

Place the cream, milk, sugar and salt in a saucepan, and place on the stove over medium-low heat. Heat just to a simmer, then remove from the heat. 

Add your chocolate into the pan with the milk mixture. Let it sit for two minutes, then whisk steadily until all the chocolate is incorporated into the milk & cream mixture. 

Lightly beat your egg, and then add it to the chocolate mixture and whisk thoroughly. The texture of the chocolate filling will thicken somewhat. 

Pour chocolate mixture into your baked tart crust.

Decrease the oven temperature to 300 degrees. Place the baking sheet with the tart on it back in the oven and bake for 12-16 minutes, until almost set- when you gently shake the baking sheet, the center of the tart should still have a little jiggle to it. 

Remove the tart pan to a wire rack to cool. Sprinkle flaky salt, such as Maldon or something similar, over the top of the tart filling. 

Allow the tart to cool- you can let it cool all the way to room temperature if you wish, or serve it slightly warm (my favorite!)

I highly recommend whipping up some lightly sweet vanilla whipped cream to serve with this tart while you wait for it to cool.

Serve this decadent chocolate dessert in nice slivers, with a dollop of fresh whipped cream.