Grease and line a tin that is about 25 x 35 cm. If you prefer your slice thinner, use a larger tin.

In a medium pot over a medium heat, melt the butter, stirring often. Remove from heat and stir in the chopped chocolate until smooth.

Whisk in the cocoa, sugar, eggs and vanilla.

Put the crushed biscuits in a large bowl and pour in the chocolate mixture. Stir until all the biscuits are thoroughly coated.

Press firmly into prepared tin and smooth the top as much as possible (wet fingers are the best tool for this) the refrigerate until set (about 2 hours).

To make the topping, melt the chocolate and butter in the microwave (or in a bowl over simmering water) and stir well to combine. Go slowly if using a microwave as white chocolate has a lower melting point than dark/milk chocolate and is therefore more likely to overheat and seize.

Pour the topping over the chilled base and spread it out with a spatula to smooth it off. Sprinkle over the smashed eggs, start with the whole ones, spreading them around evenlyish, then the halves, and then sprinkle over the crumbs at the end. Push the larger whole eggs in with the palm of your hand to ensure they are swell stuck, and refrigerate for another hour.

When topping is set firm, cut into squares or fingers with a large sharp knife. Embrace the higgledy-piggledy nature of the pieces as it’s almost impossible to cut it up evenly. Store in the fridge in an airtight container, with baking paper between the layers, for up to one week.