Preheat oven to 200C/400F/Gas 6 and line a baking sheet with parchment paper.

To make the streusel: Place flour, powdered sugar, and cinnamon in a bowl and stir to blend together. Add the melted butter and mix until it starts to form small pea-sized pieces.

Tip the streusel onto the prepared baking sheet in an even layer and place in the oven for 20 minutes, or until golden brown - turning halfway through to bake evenly. Remove from oven and leave to cool.

To make the crust: Place the flour and powdered sugar into a bowl and give it a stir to combine, then add the melted butter and stir to form a dough ball.

Press the dough into an even layer in a square (9x9") baking dish.

Place in the oven at the same temperature as the streusel and bake for 20 minutes. Remove when cooked and set aside.

Reduce oven temperature to 180C/350F/Gas 4.

To make the pumpkin filling: Place the pumpkin, eggs, milk, and vanilla, and pumpkin pie spice into a bowl, and using a stand or handheld mixer, and blend to combine for 1 - 2 minutes.

Pour the pumpkin filling on top of the baked crust, and place it back in the oven at the lower temperature and bake for 45 minutes or until a toothpick in the center comes out clean.

Remove the dish from the oven and place on a wire cooling rack.

Spread the streusel in an even layer on top of the pumpkin and leave to cool for at least 2 hours before cutting into 3x3" bars (or whatever size you like!)

Serve with whipped cream and a sprinkling of cinnamon. Enjoy!