Preheat the oven to 350 degrees F.

Place the butter and sugar into a food processor and process until smooth, scraping down the sides.

Add the egg and mix until well combined.

Add the flour in two batches and mix until a dough forms. Scrape down the sides as needed.

Press the dough evenly into a 9-inch tart pan. I like to start with the sides, then press the rest of the dough into the bottom of the pan.

Freeze for 25 minutes.

Poke holes all over the bottom of the crust.

Bake for 10 minutes, or until the mixture is no longer glossy. Allow to cool completely.

When the crust is cool, make the filling by adding the chopped chocolate to a large heatproof bowl.

Add the heavy cream and butter to a small saucepot over medium heat and bring to low simmer, stirring occasionally.

Once at a simmer, pour the mixture over the chopped chocolate and let it sit for 5 minutes.

Whisk to combine until smooth; this may take a couple of minutes.

Pour the ganache into the crust. I shake it a little bit to distribute evenly.

Allow to set overnight at room temperature or in the fridge for about 2-3 hours.

Slice and serve with any garnishes you wish.