Preheat the oven to 350° and lightly grease a 9-inch round cake pan with canola oil.
In a small bowl, combine 3 tablespoons of the espresso and the flaxseed meal and allow to thicken for 3 to 5 minutes. In another small bowl, whisk together the flour, sugar, cocoa powder, baking powder, baking soda, salt, and xanthan gum.
Pour in the canola oil, vanilla, and remaining 1⁄2 cup of espresso. Stir with a wooden spoon until thoroughly combined and smooth. Fold in the chocolate chips.
Pour the batter into the prepared pan and bake for 40 minutes, or until the brownies are firm and a toothpick inserted in the center comes out clean. Let the brownies cool completely in the pan on a rack before cutting them into triangles.
Store the brownies, tightly wrapped and refrigerated, for up to 5 days.
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Allergy-Free Desserts. Excerpted by permission of John Wiley & Sons, Inc. All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.