Preheat oven to 350°F. Line a baking sheet with parchment or a Silpat. Set aside.
Whisk millet flour, brown rice flour, sourgum flour, baking soda, xanthan or guar gum, salt, cinnamon and cardamon together in a bowl. In a smaller bowl, cream together shortening and brown sugar until fluffy. Add eggs, mixing thoroughly. Whisk in applesauce and extracts.
Add dry ingredients to the mixing bowl with the wet ingredients and mix until combined.
Scoop dough onto the lined baking sheet. Using wet hands form the dough into a log approximately 1 inches in height and about 6 inches wide. Bake at 350°F for 25-30 minutes (or until middle is dry when you insert a toothpick). Remove from oven and allow to cool (approximately 30 minutes). Lower oven to 300°F. Using a serrated knife, cut biscotti cross-wise, making ½ to ¾ inch wide pieces. Put slices back onto the baking sheet leaving a bit of space between slices.
Bake at 300°F for 10 minutes, then flip over and bake 10 more minute. Watch closely to avoid burning biscotti. Cool biscotti on a cooling rack.
When cooled, mix powdered sugar and milk substitute a bit at a time until you reach desired consistency. Mix in cardamon. Drizzle on cooled biscotti and let dry until glaze is firm.
Recipe by Grain Mill Wagon at https://www.grainmillwagon.com/gluten-free-dairy-free-apple-cardamom-biscotti/