Chocolate Layers - Brownies, salted caramel mouse and a chocolate ganche

As K suggested this would be fabulous cut into much smaller squares and served as petit fours, though I served it in thin slices - it's very rich and totally yummy. I found in on another blog, the excellent Tartelette - I've altered it only very slightly.

Dark Chocolate Walnut Brownie base:

3oz tablespoons unsalted butter
6oz 70% chocolate
2 3/4 oz plain flour
1/4 teaspoon baking powder
1/8 teaspoon salt
2 large eggs
5oz caster sugar
2 teaspoons pure vanilla extract

Preheat oven to 180°. Line an 9x13 inch baking tray with baking paper, leaving an overhang on to sides so you can lift the whole thing out once completed.

Melt together butter and chocolate in a heatproof bowl set over a pot of simmering water. Remove the bowl from heat and stir until smooth. Set aside to let it cool slightly.
Beat the eggs with the sugar and vanilla until pale and thick (about 3 minutes) then add in the cooled chocolate mixture and beat again.
Add the flour, baking powder, and salt and slowly mix until just incorporated.
Transfer the batter to the prepared pan, and smooth top with an spatula. Bake until a cake tester inserted into brownie between edge and center comes out with a few crumbs about 20 minutes, depending on your oven (Do not overbake!). Let cool completely in the tin before proceeding.

Milk Chocolate and Salted Butter Caramel Mousse Layer:

3 1/2 oz caster sugar
2 Tbsp water
1 oz salted butter
10 floz double cream, divided into 7floz and 3 floz
6 oz mix of milk and semi sweet chocolate

Keep the 7 floz of cream chilled in fridge. Microwave the remaining 3 floz and the butter until it is fairly hot and the butter is melted. It will be added to the caramel and by being hot it will prevent the caramel from seizing on you and clumping up.
Melt the chocolate in a heatproof bowl set over a pot of simmering water . Set aside.
In a heavy bottomed saucepan, add the sugar to the water over medium high heat and cook, without stirring until you get a dark brown caramel. Take the pan off the heat and add the butter and cream mix. It will bubble like mad but it will not run over....if the butter and cream are not cold the bubbling will be minimal and short lived. Stir with a wooden spoon to smooth the caramel if necessary. Let it cool to lukewarm.
Add the caramel to the chocolate and stir until smooth - if it seizes (which is may) mix in a small amount of vegetable oil to save it and continue.

Whip the remaining cream to soft peaks. Fold 1/3 of the this whipped cream to the chocolate/caramel to loosen it up and then add the remaining whipped cream. Spread over the brownie base and refrigerate until completely set. The mousse is quite dense as there are no egg whites involved so don't worry if it looks like it won't set - it will

Dark Chocolate Ganache:
5 floz cup heavy cream
6oz 70% chocolate

In a medium saucepan, bring the cream to a simmer, remove from the heat. Add the chocolate to the cream and let sit for 5 minutes. Slowly stir the heavy cream and chocolate until they come together and form a shiny ganache. Let cool. You want the ganache to still be pourable but not too warm that it will melt the mousse.Spread it over the caramel mousse and refrigerate until set.

To serve: lift the dessert out of the pan using the overhanging paper sides and trim the sides with a sharp knife (heated under hot water and wiped dry), cut into the desired number of servings and enjoy. You can sprinkle with the chopped walnuts - or just dust with cocoa.