1.Preheat oven to 160°C. Grease 23cm-square cake pan and line base with baking paper.
2.Combine butter, 2 tsp coffee powder, hot water, chocolate and 1 cup sugar in medium saucepan. Stir over low heat until chocolate is melted. Place chocolate mixture in a large bowl and cool 5 minutes.
3.In two batches, whisk in sifted flours and 2 tbs cocoa powder, then whisk in egg and essence. Pour mixture into prepared pan.
4.Bake about 40 minutes. Stand cake in pan 5 minutes, before turning onto wire rack to cool.
5.Meanwhile, combine the water and remaining sugar and coffee in a medium saucepan. Stir over heat, without boiling, until sugar is dissolved. Bring to a boil and boil uncovered without stirring for 5 minutes. Remove from heat, stir in marsala and cool. Reserve 1/3 cup of the coffee syrup.
6.Split cake in half horizontally. Place halves, crust- side up, on a tray. Brush with remaining coffee syrup. Cover and refrigerate 3 hours or overnight.
7.Cut each cake half into eight equal pieces. Combine mascarpone, cream and reserved coffee syrup in medium bowl; whisk gently until mixture thickens slightly.
8.Assemble tiramisu among eight serving dishes. Place a piece of cake on each dish, top using half of the mascarpone mixture. Repeat, using remaining cake and mascarpone mixture. Top with raspberries; dust with remaining sifted cocoa powder.