Preheat your oven to 350 degree F and line a 9x13inch baking pan with parchment paper. Set aside.
In the bowl of your stand mixer with paddle attachment fixed, cream together the butter, sugars, and salt for about 2 minutes. Add the vanilla extract and egg, and mix until combined. In a separate medium bowl, whisk together the flour and baking powder. Gradually add the dry mixture to the wet. Mix until combined. Stir in the chocolate chips. Alternatively, all of this can be done with a handheld electric mixer.
Scoop the mixture into the prepared pan and press down to even things out. Place the pan in the preheated oven and bake the blondies for 22-30 minutes or until a toothpick comes out "generally" clean. Remove from oven and let cool for at least 30 minutes before topping with meringue (see recipe below).
For the meringue, place the egg whites in the bowl of your stand mixer with whisk attachment fixed. Alternatively, this step can be completed with a handheld mixer. Beat on medium-high speed until peaks just start to form. With the mixer set on low, gradually add the sugar. Increase the speed back to medium-high, and mix until very stiff peaks form and the meringue looks glossy. Add the vinegar, and mix for just a few seconds to incorporate.
Once the blondies have cooled, spread the meringue on top in an even layer. If you wish to have that "toasted" look, use either kitchen torch or your oven's broiler. If you do choose to use your broiler, have a very careful and watchful eye as the meringue can quickly go from brown to burnt in just seconds. Top with golden grahams cereal, Hershey bars, and mini marshmallow if desired. Cut into squares and enjoy!
These s'mores blondies will keep for a couple of days in the refrigerator, but are best served the day of baking.