Warm 1 tbsp olive oil in a large pan over medium heat.
Add the chopped onion, celery, carrot and mushrooms. Cook 4-5 minutes until the vegetables soften. If there’s a lot of liquid in the pan (likely from the mushrooms), continue cooking until the liquid evaporates.
Add garlic and cook for another 1-2 minutes.
Next, add all the remaining ingredients except for the gluten flour. This includes 2 C cooked lentils, ½ C cooked quinoa, ½ C chopped walnuts, 2 tbsp ground flaxseed, 2 tbsp ketchup, 1 tbsp BBQ sauce, 1 tbsp apple cider vinegar, 1 tbsp maple syrup, leaves from 3-4 sprigs fresh thyme, 1 tsp Herbamare seasoning, 1 tsp smoked paprika, ½ tsp dry ground sage and ¼ tsp black pepper.
Stir until well combined.
Sprinkle ¼ C gluten flour over the surface of your lentil-vegetable mixture. Carefully stir in the gluten flour until it’s evenly mixed throughout.