Rich and decadent, Mark’s wedges of brownie baked on a biscuit base have a final flourish in the Italian meringue topping that turns them from treat to heavenly dessert – truly s’mores in cake form. If you don’t have time to make the meringue, you could serve the brownies with cream or ice cream, if you like.
Begin the brownie mixture. Place the butter and chocolate chips in a glass bowl set over a pan of barely simmering water. Allow to melt, then stir to combine, stir in the espresso powder and set aside to cool.
Heat the oven to 200°C/180°C fan/400°F/Gas 6.
Make the cookie base. Place the butter and sugars in the bowl of a stand mixer fitted with the beater attachment and beat on a low speed until combined. Add the egg yolk and vanilla and beat until smooth.
Add the flour, salt, bicarbonate of soda, baking powder and chocolate chunks and mix to a soft, crumbly dough. Press the mixture into the base of the tin, then chill while you finish making the brownie.
Place the sugars, vanilla, eggs and salt in the bowl of a stand mixer fitted with the paddle attachment. Mix on medium speed for 2–3 minutes, until smooth and slightly paler in colour.
With the mixer on low speed, gradually add the cooled chocolate mixture until fully combined. Sift in the cocoa powder and flour and, using a large metal spoon, stir until smooth. Then, fold in the white and milk chocolate chunks.
Remove the cookie base from the fridge and pour the brownie mixture evenly over the top. Bake for 15 minutes, then remove the tin from the oven and gently drop it onto the work surface three or four times to remove any large air bubbles. Return the tin to oven and bake for a further 15–20 minutes, until the edges just start to come away from the side of the tin and a skewer inserted into the centre comes out with a little mixture attached, but is not too wet. Remove from the oven and leave in the tin to cool completely.
Make the Italian meringue topping. Place the caster sugar and 25ml of water into a small pan on a low heat. Leave, without stirring, until the sugar dissolves and reaches 118°C/244°F on the sugar thermometer.
Meanwhile, place the egg whites in the bowl of a stand mixer fitted with the whisk attachment. Whisk on medium–low speed until foamy, then keep whisking at the lowest speed while you finish the syrup.
When the sugar syrup reaches 118°C/244°F, turn the stand mixer up to medium speed and whisk the whites again until they hold soft peaks. Then, once the syrup reaches 120°C/248°F, slowly pour it onto the egg whites, being careful not to pour directly onto the whisk. Turn the speed up to high and whisk for 7–8 minutes, until the bowl is cool and the mixture is smooth and glossy. Place the meringue in the large piping bag fitted with the ribbon nozzle.
Using a hot, dry knife, cut the cake into 10 equal wedges. Arrange the slices on a plate, spacing them slightly apart. Pipe the Italian meringue on top of each slice, then use the kitchen blowtorch to briefly colour the topping until lightly golden. Sprinkle with cranberries to finish. (You can bake any leftover meringue in little mounds on a baking tray at 120°C/100°C fan/250°F/Gas ½ until dried out.)