Preheat oven to 350 degrees Fahrenheit.

In a mixing bowl, cream together 1/2 cup margarine, 1/2 cup packed brown sugar, and 1 cup flour until well combined.

Press the mixture evenly into a greased 9x13 inch baking pan.

Bake the bottom layer in the preheated oven for 8 minutes.

In a separate mixing bowl, combine 1 cup packed brown sugar, 2 beaten eggs, 1 1/2 teaspoons vanilla extract, 1/4 teaspoon salt, 2 tablespoons flour, and 1 teaspoon baking powder.

Mix the ingredients until a smooth batter forms.

Pour the batter evenly over the baked bottom layer.

Sprinkle 1 1/2 cups of chocolate chips evenly over the top of the batter.

Return the pan to the oven and bake for an additional 20 minutes, or until the top is golden brown and the center is set.

Let cool completely before cutting into bars.