For the Cake:
325g (2 1/4 cups) plain flour
2 teaspoon baking powder
1 teaspoon baking soda
1/2 teaspoon fine sea salt
180g (3/4 cup) smooth peanut butter
85g (6 tablespoons) unsalted butter, at room temperature
110g (1/2 cup) caster sugar
110g (1/2 cup) firmly packed brown sugar
1 teaspoon vanilla extract
3 eggs (See *Note above)
285ml (1 cup plus 2 tablespoons) buttermilk

For the Frosting:
250g (8 oz) cream cheese, at room temperature
125g (1/2 cup) unsalted butter, at room temperature
100g (1/3 cup plus 2 tablespoons) smooth peanut butter
Pinch fine sea salt
250g (2 cups) icing sugar
2 teaspoon vanilla extract

For the Ganache:
100g (3 1/2 oz) dark chocolate, finely chopped
75ml (2 1/2 fl oz) cream
Chopped toasted peanuts