Add the flour, brown sugar, spices, and salt to a large mixing bowl and whisk well to combine. Add cubed, cold butter, and work the butter into the flour mixture using your fingers. Once the butter has been worked to basically disappear into the mixture, set the bowl aside.

Add the egg yolk to the heavy cream, and whisk until smooth. Slowly drizzle the cream+yolk into the flour/butter mixture, tossing with a fork while you drizzle to promote even coverage. After all the liquid has been added, use your hands to slightly knead the dough until it comes together into a slightly shaggy ball of dough. Press the dough into a disc shape, wrap in plastic, and place into the fridge to cool for at least 2 hours.

Remove the dough from the fridge, and roll it out to be about a 13” wide circle. Transfer the dough into the tart pan (see write up for instructions and pictures on easy transferring). Firmly press the dough into the pan, remove the excess overhang, prick the bottom of the crust with a fork, then place into the freezer for 20 minutes.

Remove the crust from the freezer, place a piece of parchment into it, and place pie weights (or dried beans) into the parchment. Place into the oven to bake for 15 minutes, then remove the parchment and pie weights (be careful that you are not pulling up the pie crust), then return back into the oven for another 20 minutes. Allow the crust to cool to room temperature.

In a large saucepan over medium heat add sugar, water and cream of tartar. Stir occasionally until the sugar has dissolved and the mixture begins to boil.

Once the mixture begins to boil turn the heat up to medium-high and allow the mixture to boil, ensuring not to stir it, until it turns amber in color (stirring the mixture will cause crystallization, so refrain from stirring).

Once the mixture has become amber in color (360°F on a candy thermometer), add the cubed butter and mix very vigorously to combine. (Be careful, however, because the mixture will bubble and rise up rapidly when you add the butter). If the butter seems to be separating from the caramel, remove it from the heat, then whisk vigorously until it comes together.

When just warm, pour the caramel filling into the cooled crust. Place into the fridge for at least 1 hour to cool.

Add chopped chocolate to a heat proof bowl.

Add cream and butter to a small saucepan over medium heat. Bring to a simmer, then remove from the heat and pour over the chopped chocolate. Allow to sit for 5 minutes, then whisk well until well-combined and smooth. Place the ganache in the fridge to cool for 1-2 hours.

Remove the filled tart from the fridge, add the chocolate ganache on top, then using a spoon smooth the chocolate across the tart, then create swoops and swirls with the spoon. Top with flaky salt. Keep cold until serving.