Photograph: Martin Poole
Preheat the oven to 180°C, fan 160°C, gas 4. Melt the chocolate over a bowl of simmering water, take the bowl off the heat; cool slightly.
Whisk the butter and sugar to combine. Gradually mix in the eggs, then the flour, melted chocolate, Brazil nuts and ginger. Tip into a lined 18cm-square tin. Bake for 25 minutes. Cool; cut into squares.
Get ahead: make the day before; they can also be frozen.