Step 1

Preheat oven to 180°C.

Step 2

Grease the base and sides of a 23cm square cake pan or a 20 x 30cm lamington pan and line with baking paper.

Step 3

Place the butter and peanut butter in the bowl of a stand mixer with the paddle attachment and beat on high until pale and fluffy. Reduce speed to low and gradually add sugar until just combined. Combine the flour, baking powder and 1/2 tsp salt and add to the butter mixture. Mix until the mixture just comes together (it will be crumbly). Transfer mixture to prepared pan and press to completely and evenly cover the base. Using a fork, prick a few holes over the base, then bake for 10 minutes or until light golden.

Step 4

Meanwhile, for the crumble topping combine the ingredients in a bowl. Using your fingers, rub the mixture together to create a crumbly, sandy texture. Set aside.

Step 5

Remove the base from the oven and spread the jam evenly over the top. Sprinkle the crumble over the jam, then place on the centre rack of the oven and continue baking for a further 25 minutes or until the top is golden brown and nuts are toasted. (You may need to increase the oven temperature for the final couple of minutes to achieve this.)

Step 6

Remove pan from the oven and allow to cool completely before pulling the peanut butter, oat and jam slice out of the pan. Slice into 16 pieces and serve with coffee or tea!