Preheat the oven to 180°C (350°F). Grease a 28 x 18cm baking tin. Line the tin well with baking paper, making sure baking paper overhangs.
Place all the base ingredients into the bowl of a food processor and pulse a few times until it forms a clumpy crumb. Pour into the lined baking tin and spread out. Press the mixture down firmly.
Bake for 12-18 minutes or until edges are lightly browned. Remove from the oven and set aside to cool to room temperature.
Add the eggs and sugar to a large bowl and whisk briefly. Add all the other ingredients and whisk again until everything is combined.
Pour the filling over the cooled base. Reduce the oven temperature to 165°C (325°F) and bake the slice for 30-35 minutes or until the centre is only just set.
Remove from the oven and allow to cool completely. Refrigerate for at least 2 hours before slicing. Sift icing sugar over the top before serving.
