Preheat the oven to /175ºC/350°F/Gas mark 4

Line a 20cm2/8-inch2 baking tin with parchment paper

Whisk together the butter, brown sugar in a medium-sized mixing bowl

Whisk in the egg and vanilla

Toss the pecan halves in the flour and set them aside

Sift over the flour, bicarbonate of soda and salt and fold in using a spatula

Fold in the chopped pecans

Spoon the dough into the prepared tin and level out and into the corners

Lay the floured pecan halves across the top, spaced evenly apart

Bake for 30 minutes until the edges begin to turn brown and come away from the sides of the tin

Remove from the oven and allow the square to cool completely in the tin on a wire rack

Lift the square out of the pan and onto a chopping board or work surface and cut into 8 equal pieces