For the brownie
Preheat the oven to 160° C.
Lightly grease a tart pan of 24-26 cm diameter and of 10-11cm height.
In a small saucepan, mix the chocolate with the butter over low heat until smooth. Set aside to cool.
In a large bowl, mix the icing sugar, brown sugar, eggs, flour, cocoa and liqueur. Then add the chocolate mixture and mix everything together.
Pour into the tart pan and bake for 25 – 30 minutes until it sets.
Let it cool in the tart pan.
For the meringue
In a metal bowl, mix the egg whites with the sugar and then place the bowl in a double boiler.
Mix with a whisk until the temperature reaches 60° C.
Pour into the mixer and beat the meringue until it sets and becomes fluffy, while at the same time, adding the liqueur little by little.
Once the brownie has cooled, unmould it and spread the meringue with a spatula or pastry bag, forming little peaks here and there. Torch the meringue lightly or place in the oven until it gets a little coloured (about a minute at 250 ° C on grill mode).
Cut into slices, and serve by pouring the extra liqueur on top.
The pastry bag may not be necessary here, but a gadget that you will find very useful for this as well as other recipes is the thermometer.