Pre-heat oven to 180C. Grease and line a 8X8 baking pan with parchment paper.
Whisk flour, baking powder and salt together.
Melt butter in heatproof bowl over simmering water, stir in sugar and gently fold in egg and vanilla.
Stir wet and dry ingredients together. Fold in chocolate chips.
Pour batter into pan and place/push Reese's peanut butter cups randomly around the mix
Scatter more chocolate chips on top and bake in the oven for about 30 mins or till the top is semi-browned and the sides pulls away from the pan.
Recipe adapted from 'The Food Librarian'