Preheat your oven to 350°F. Grease or line an 11 x 13 x 1 ½ inch baking pan with parchment paper or give it a light spray of cooking spray. This makes it much easier to lift the blondie brownies out of the prepared pan once they are baked.

Mix the dry ingredients. In a separate bowl, whisk together the flour, baking powder, and salt. This flour mixture ensures your blondie batter bakes evenly.

Combine the wet ingredients. In a large bowl, cream together the butter and brown sugar until smooth. Add the eggs one at a time, then stir in the vanilla extract.

Fold in the flour mixture. Gently stir until just combined, do not overmix.

Add the mix-ins. Fold in the chocolate chips (or chunks) and walnuts. Use a sharp knife to chop larger pieces if needed.

Spread the batter. Pour into the prepared pan and smooth the top.

Bake. Place in the oven and bake for about 25 minutes, or until the top is golden brown and a toothpick inserted into the center comes out mostly clean.

Cool. Let the blondies rest in the pan for 10 minutes, then lift them out onto a wire rack to cool completely before cutting into bars.