Preheat oven to 350°F. Line a 13x9 baking dish with parchment paper. Set aside.
In a large mixing bowl, beat together the shortening, butter, and sugar until creamy. Beat in the whole egg, and the two egg YOLKS.
Slowly add in the flour, baking powder, and salt. Combine until fully blended.
Press batter into prepared baking dish. Top with marshmallows and chocolate chips.
In a separate clean and dry mixing bowl, beat the two egg whites until stiff. Fold in the brown sugar and pour over the stop of the bars. Spread gently, making sure it touches the sides of the pan (this will help it rise during baking, and not shrink).
Bake for 35-40 minutes, until the meringue on top is lightly browned. Remove from oven and cool completely.
Cut into bars and enjoy. We prefer to keep these chilled in the refrigerator, they taste great cold!
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