Coat an 8-inch baking
pan with cooking spray; line bottom of the pan with parchment or wax paper. Wrap outside of pan with aluminum foil.
Place ¾ cup sugar and
eggs in a mixing bowl and beat with a hand blender at high speed for 7 minutes.
Mix cornflour, cocoa
powder and salt in a small bowl.
Put orange juice,
Triple Sec, 1 tbsp hot water, salt, and chocolate in a another mixing bowl, place the bowl in the microwave at high for 1 minute or till almost melted, stirring every 20 seconds till smooth. Add cornflour mixture and whisk till smooth.
Gently stir in ¼ egg
mixture into chocolate mixture and then fold into remaining egg mixture.
Pour the batter into
prepared pan. Place pan in a 13 x 9-inch baking tray; add hot water in the tray to a depth of 1 inch.
Place the baking tray
in the preheated oven and bake for 20 minutes or until the top is set.
Remove the baking
tray from oven, lift out the baking pan from the water bath and cool for 5 minutes on a wire rack. Loosen cake from sides of pan with a narrow metal spatula; cool down to room temperature. Cover and chill at least 4 hours or overnight.
Sprinkle ½ cup
powdered sugar and orange rind just before serving, if desired.