Begin by creaming the butter and sugar together until light and fluffy.
Next, gently fold in the remaining ingredients.
To prepare the ground pistachios, place them in a food processor and pulse until finely chopped.
Set aside half of the ground pistachios for the cake batter.
Use the same food processor to make the crumble with the remaining pistachios.
Layer the cake batter and crumble in a baking dish.
Finally, place the dish in the oven to bake.
