Begin by melting 1/2 cup of butter in a microwave-safe bowl. In a large mixing bowl, sift together 1 ½ cups of flour, ½ cup of cocoa powder, ¼ cup of powdered sugar, and a pinch of kosher salt. Combine the melted butter with the dry mixture, forming a dough. Press this dough firmly into the base and up the sides of a tart pan. Chill the crust in the refrigerator for 15 minutes to firm up.

Preheat your oven to 375°F (190°C). Once the crust has chilled, remove it from the refrigerator and bake it for 12 minutes until set. To ensure a crisp crust, gently brush the inside with a beaten egg white and return it to the oven for an additional minute.

While the crust bakes, heat 1 cup of heavy cream and ¼ cup of corn syrup in a saucepan over medium heat. Stir until it reaches a gentle simmer, then remove the pan from heat. Pour this hot mixture over 1 ½ cups of semi-sweet chocolate chips in a mixing bowl, and let it sit for 2-3 minutes. Now, add 3 beaten eggs to the chocolate mixture and whisk until smooth and silky.

Reduce your oven temperature to 325°F (160°C). Carefully pour the chocolate custard filling into the pre-baked tart crust, smoothing it out for an even surface. Bake the Chocolate Custard Tart for 35-40 minutes or until the edges are set, but the center still has a slight jiggle.

Once done, remove the tart from the oven and let it cool to room temperature in the tart pan. After cooling, melt ½ cup of white chocolate to create a beautiful drizzle. Use a fork to swirl the melted white chocolate on top of your tart.