Make the tart dough by combining flour, salt, and sugar in either a mixing bowl or a food processor.
Add your butter either by hand (crumbling the cold butter into the flour until it your butter is broken down into smaller than pea size chunks or it resembles sand) or in the food processor (add your butter and pulse until the mixture resembles sand).
Add ice water (or just very cold water) and pulse or combine by hand until the dough starts to stick together. It’s okay if it’s still a little crumbly, but if it’s not coming together at all, add as many tablespoons of ice water until the dough comes together.
Wrap up your dough in plastic wrap and chill for at least 30 minutes. Towards the end of the resting time, preheat the oven to 190 °C or 375 °F
Prepare the marzipan filling by combining almond flour, powdered sugar, egg whites, and almond extract in a bowl.
Mix using a spatula until it forms a smooth paste (it will remain sticky!). You can also combine in a food processor! If it seems dry, you can add a little bit of water!
After the dough has rested, begin rolling out dough on a well floured surface. We tend to roll the dough, then rotate it ninety degrees, adding more flour underneath, and continuing to roll. This also helps keep it a round shape!
Roll into a 12" circle, about ⅛" to ¼" thick. We used a 10" tart pan for this recipe!
Prepare a tart pan by buttering the sides and the bottom and adding a piece of parchment paper to the bottom.
Roll the dough onto the rolling pin, making sure it doesn't stick to itself by adding flour as needed. This will help transfer it to the tart pan.
Transfer to the tart pan by unrolling it across the pan.
Lower the dough into the edges of the pan. Press down the corners gently, trying not to stretch the dough. If you need to patch any holes or add more dough to the edges to fill the fluted edge, just press any excess dough onto the hole or thin edge!
Clean up the edges by removing any excess dough by running a knife along the edge.
Put the tart in the freezer for about 5 minutes to cool down the butter in the dough from working with it.
Add marzipan filling to the tart,
Spread the filling evenly across the base. You can use an offset spatula to make it level, but don't worry too much about the surface being perfect!
Bake the tart at 190 °C or 375 °F for 35-45 minutes, until the crust is golden, and the top of the marzipan is also lightly golden. It may puff up slightly, but it should fall when it cools!
Remove from the oven and let the tart cool on a wire rack. If making chocolate ganache, follow the next step right after taking the tart out of the oven!
Heat up heavy cream until just below boiling. We usually do this in a liquid measuring cup in the microwave, but feel free to use a pot on the stove. Add in the chocolate (if using large chunks, make sure to chop it into smaller pieces!) and let it sit for 5 minutes.
Stir the mixture well until the chocolate melts and it's totally smooth. If the chocolate doesn't fully melt, pop it in the microwave for 5 seconds at a time until all the chocolate has melted.
Let the ganache set at room temperature until it thickens enough to either spread over the top, or pour over like an icing where it won't run off the sides. You could put it in the fridge, but it can harden pretty quickly in the cold, so make sure to keep an eye on it!
Once the tart has cooled, you can remove the edge of the pan. Pour or spread the ganache on top of the tart.
Make sure the ganache reaches all the way to the edge!
Add sliced almonds and flaky salt for decoration.
Slice and enjoy! If the ganache was runny when you poured it on top, it should set at room temperature. We do usually keep this in the fridge if we don't eat the whole thing within a day or so.