Spray a 9x13 baking pan lightly with cooking spray. In a large bowl cream together shortening, butter, granulated sugar, 1 whole egg plus 2 yolks and vanilla until smooth.
Add in flour, baking powder and salt and mix until just combined. Spread in prepared pan.
Top with chocolate chips and mini marshmallows.In a clean mixing bowl with whisk attachment on your mixer, beat the 2 remaining egg whites until stiff peaks form, about 2 minutes on high.
Fold in 1 light brown sugar and stir until combined and there are no lumps.
Spread on top of chocolate chips and marshmallows. Bake 30-35 minutes until top is golden brown.Allow to cool completely before cutting into squares
Recipe by Kitchen Belleicious at https://kitchenbelleicious.com/2012/12/10/mud-hen-bars-with-brown-sugar-meringue/