Preheat oven to 350°F (180°C).

1. In a large bowl or plastic bag, combine yellow pea flour, potato starch, brown sugar, baking powder, xanthan gum, salt and walnuts. Mix well and set aside.

2. In a large bowl, microwave shortening and chocolate on Medium for 3 minutes or until partially melted in a saucepan over hot water. Stir until melted. Add eggs, one at a time, blending after each. Stir in vanilla extract. Slowly add the dry ingredients, stirring until combined. Spread evenly in prepared pan. Let stand for 30 minutes. Bake in a preheated oven for 20 to 25 minutes or until a cake tester inserted in the center still has a little moist crumb adhering to it. Let cool for 15 minutes on rack. Meanwhile, prepare glaze, if desired.

3. Glaze: In a small bowl, over hot water, partially melt the shortening and chocolate. Remove from heat and continue stirring until completely melted. Spread on warm brownies. Cool completely before cutting into squares.

Variation: Substitute an equal amount of whole bean flour for yellow pea.