Step 1

Preheat oven to 180 c or 350 F.

Step 2

Line an 8 x 8 inch square pan with parchment paper or aluminium foil , leaving enough overhang on the sides.

Step 3

Melt the butter in a saucepan.

Step 4

Take off the heat and mix in the brown sugar and vanilla extract .

Step 5

Cool for 5 minutes and whisk in the yoghurt until smooth.

Step 6

Add in the flour, baking powder , soda and salt. Whisk together until incorporated.

Step 7

Fold in the chocolate chips , if using.

Step 8

Spread batter into the prepared pan and bake at 180 c/ 350 F for 28-32 minutes.

Step 9

Cool completely in pan , remove slab and slice with a sharp knife!