A chocolate cookie base,
190g/6.7 oz cookies - I use chocolate bourbons but you could use digestives/graham crackers
2 tablespoons sugar
113g/4 oz butter
60g/2 oz water
30g/1 oz butter
250g/8.8 oz sugar
90g/3 oz cocoa powder
85g/3 oz vegetable oil
2 teaspoons vanilla extract
1 large egg yolk
1 large egg
1/8 teaspoon bicarbonate soda
1/2 teaspoon salt
1 tablespoon corn flour/cornstarch
60g/2.1 oz plain/all purpose flour
115g/4 oz chocolate chips
100g/3.5 oz sugar
3 tablespoons water
5 large egg yolks
225g/8 oz butter - room temperature
1 teaspoon vanilla extract
Preheat your oven to 350F/180C/Gas 4.
Line a 9" square pan with tin foil, spray with vegetable oil.
Crush the cookies to crumbs and mix with the sugar.
Melt the butter and pour into the cookie crumbs, mix to combine.
Tip into the prepared pan and press to make an even base.
Bake for ten minutes.
To make the brownies, pop the water, butter, sugar and cocoa powder into a saucepan and cook over a medium heat for two or three minutes until combined.
Add the vegetable oil and vanilla extract. Cook for a further minute, stirring until combined.
Remove from the heat and cool for five minutes.
Add the egg and egg yolk, whisk to combine.
Add the bicarbonate soda, salt and cornstarch into the flour and then fold into the wet ingredients until just combined, don't over mix.
Fold in the chocolate chips.
Spoon over the cookie base.
Bake for 25 minutes.
Allow to cool in the tin.
To make the French buttercream.
Put the sugar and water into a saucepan and heat over a low heat, stir until the sugar dissolves.
Increase the heat and bring to the boil.
At the same time, in a mixer beat the egg yolks until thick and foamy.
Cook the sugar and water syrup until it reaches 240F. Immediately remove from the heat.
Keep the mixer running and very slowly drizzle the hot syrup into the bowl with the yolks.
Continue whisking until the bottom of the bowl is cool to touch and the yolk mixture has come to room temperature.
Add in the butter a small piece at a time, allowing the mixer to incorporate each piece of butter before adding the next. Add the vanilla extract and salt.
Continue whisking until the buttercream is smooth, this will take about five minutes or so.
Spread onto the brownie.
Decorate with sprinkles if you would like to.