For the bread:
Step 1: Preheat the oven to 400 degrees F. In a medium-sized mixing bowl, combine the cornmeal, gluten-free flour, baking soda, salt, sugar and cumin. Mix to blend evenly, and set aside.
Step 2: In another medium-sized mixing bowl combine the buttermilk, olive oil, butter, eggs and lemon juice. Use a whisk to whip everything together, just until it's smooth.
Step 3: Make a well in the center of the dry ingredients and pour in the wet ingredients. Fold everything together and mix to blend evenly. Now pour the mixture into an approximately 8 X 8 X 2-inch baking dish. (I find that there's enough oil in the batter to prevent sticking, but if you want to be sure, you can lightly grease the pan with butter or olive oil.)
Step 4: Bake in the preheated 400 degree F oven until the bread is golden brown along the edges and no longer jiggles, about 25 minutes.
Step 5: Remove the bread from the oven and let it sit for at least 4 hours to cool completely. (If you don't do this, it will likely crumble when you cut it for the stuffing.)
Step 6: When you are ready to use the bread, use a dull knife to go along the edges of the pan, and invert it onto a clean, dry cutting board.
Step 7: Preheat the oven to 400 degrees F (again). Cut the bread into approximately 1-inch cubes and place them on a foil-lined baking sheet. Set aside.
For the stuffing:
Step 8: Coat the bottom of a large sauté pan with olive oil and place it over medium heat.
Step 9: Add the onion and celery and cook until soft, stirring periodically, about 7 minutes. Turn the heat to medium-high, add the mushrooms, and continue to sauté until the mushrooms are beginning to brown. Then add the sage, salt and pepper and stir to blend. Set aside.
Step 10: Place the cubed cornbread in the preheated 400 degree F oven and toast them until most of the cubes are golden brown, about 20 minutes. (Ideally, do this step while the vegetables are sautéing.)
Step 11: In a large bowl, combine the toasted cornbread with the vegetable mixture. Add ¼ - ½ cup stock, depending on how moist you like your stuffing.
Step 12: Warm the stuffing, covered, in a 325 degree F oven, about 15 minutes before serving.
Recipe note: To save time, if you have a gluten-free cornbread or other gluten-free soft bread that you like, feel free to try it.