1 Preheat your oven to 180⁰C/gas mark four, and grease and line a 28x18cm tin.
2 Melt the chocolate and butter either in a glass bowl over a pan of simmering water or in a microwave. Just take care it doesn’t catch.
3 Once the chocolate mixture’s completely smooth, mix in the cocoa powder. Then set to one side to cool.
4 Crack the eggs into a little bowl and give them a quick whisk (a fork will do) until they’re slightly frothy. Now you can add the sugar, beating until the mixture’s thick and mousse-like.
5 Pour the melted chocolate into the mousse and fold gently. If you want to add crushed chocolate eggs or nuts, now’s the time.
6 Tip the brownie mix into your tin and bake it for 30 minutes until it’s just set in the centre (that way it stays lovely and moist). It’ll continue to cook slightly when it’s out of the oven. Leave it to cool for ten minutes or so before transferring it from the tin to a wire rack to cool completely.
7 While it’s cooling, you can melt your white chocolate. Like in step two, be extra careful not to leave the bowl unattended – white chocolate has no cocoa solids so it can seize very suddenly.
8 Drizzle the chocolate, once melted, across each brownie and add whatever decorations you’d like.