Using an electric mixer, beat together the brown sugar, butter, peanut butter, vanilla and eggs until combined and creamy.
In a separate bowl sift together the flour, baking powder, baking soda and salt. Slowing beat that into the wet mixture until a smooth batter is formed.
Cut 24 Reese Minis in half. Add those and the chocolate chips into the batter.
Pour the batter into the 13x9 pan and bake in a 350F oven for 25-30 minutes.
Remove from the oven and immediately press the remaining peanut butter cups onto the top of the blondie in even rows.