Preheat the oven to 350°F.

In a medium bowl, combine the flour, sugar, cornstarch, and salt.

Add the melted butter, olive oil, and milk. Stir until all of the ingredients are well combined and a crumbly dough forms.

Press the dough into your tart shell, starting from the sides and then moving to the center. The sides should be slightly thicker than the botttom.

Use a fork to prick the bottom of the tart shell.

Bake the tarrt shell until golden-brown and crisp, about 20-25 minutes.

Remove the tart shell from the oven and allow to cool.

While the tart shell cools, add the dark chocolate pieces and heavy cream to a medium sized saucepan and place over low heat.

Stirring frequently to prevent burning, allow the chocolate to melt completely.

Once the chocolate is melted, remove the pan from the heat and stir in the Kahlua and vanilla extract.

Pour the chocolate Kahlua filling into the baked tart shell.

Place the tart in the refrigerator to set for a couple of hours.

Sprinkle with flakey sea salt and/or drizzle with melted white chocolate as garnish.

Enjoy!