Preheat your oven to 350°.
Line a 9 x 9-inch baking pan with nonstick foil, leaving enough overhang to help you lift the blondies from the pan when they're done.
In a medium bowl, whisk together the flour, baking powder, and salt.
In another bowl, whisk melted butter and brown sugar until combined. Add eggs and vanilla extract, mixing well.
Using a rubber spatula, fold the dry ingredients into the egg mixture until just combined; do not overmix.
Fold in chocolate chips and M & M's and pat the batter into the prepared pan.
Push in a few M & M's on top of the dough to garnish.
Bake until the top is shiny, cracked, and light golden brown, about 27 to 30 minutes; do not overbake.
Cool on a wire rack to room temperature.
Remove bars from pan using foil and cut to serve.
