Melt the butter in a medium size heavy saucepan over low heat.
Add the sugar, cocoa, Kahlua, cream & salt.
Stir over moderate heat until the mixture comes to a boil.
Add the instant coffee & stir to dissolve.
Reduce the heat & let simmer for 5 minutes.
Remove from the heat & stir in the vanilla.
Preheat the oven to 150C.
Melt butter in a double boiler & stir in the cocoa.
Remove from the heat then stir in sugar.
Break eggs into the mixture one at a time, then add flour & stir to combine.
Add walnuts, vanilla & salt.
Stir to combine all the ingredients.
Pour into a Swiss roll pan .. 30cm x 25cm that has been greased & lightly floured.
Bake for approximately 20 minutes in convection oven.
(Rotate pan 180° after 10 minutes if not cooking in convection oven).
Do not overcook.
Leave the brownies to cool in the pan for a few minutes then turn out onto cooling rack.
Pour the frosting over top of brownies straight away.
Cool for approximately 40 minutes at room temperature, or refrigerate to cool before cutting.
Cut into 10cm x 10cm x 14cm triangles and slice each triangle in half through the middle.
Make the coffee with hot water & add to the (room temperature) butter, cocoa & icing sugar.
Stir until smooth.
Pipe about 2 tablespoons of the mocha chocolate sauce in a zig-zag pattern on each serving plate. Place the bottom half of a brownie triangle on top, then a scoop of vanilla ice-cream in the centre of the triangle. Drizzle more sauce over the ice-cream and place the frosted half of a brownie triangle on top of the ice-cream.