Sift the powdered sugar and cocoa powder into a bowl. Add the graham cracker crumbs and mix well. Pour the melted butter in and using a fork, stir until the butter is well distributed and the mixture is like wet sand.
Dump the graham cracker mixture into your tart pan. Use a flat bottomed glass or measuring cup to press the mixture evenly up the sides and across the bottom of the tart pan. Place in the refrigerator to chill.
In a large mixing bowl, add the finely chopped chocolate, the instant espresso, sea salt and butter.
In a small saucepan or kettle, boil some water. Measure out 7 oz (by weight) into a measuring cup, then add the brandy. Pour the liquid over the chocolate to submerge. Cover with a plate and let it sit for 3 minutes. Stir the chocolate mixture until it is well combined and the butter and chocolate has completely melted. It should be smooth and glossy.
Pour the chocolate ganache into the chilled tart shell. Use a pick to pop any large bubbles on the surface. Let the tart cool for 30 minutes at room temperature.
Warm 3 oz of white chocolate and 1 oz of water in a microwave safe bowl on 50% power in 30 second increments until smooth and melted. Dollop this on top of the tart. Using a wooden skewer, drag the white chocolate through the surface of the ganache to create big, organic swirls.
Allow the tart to set at room temperature for 6 to 8 hours, or in the refrigerator for 2 to 3 hours.
Garnish the tart with fresh raspberries, white chocolate (chips or curls) and mint.