Instructions:
- Combine flaxseed meal and water in a small bowl; set aside for 5-10 minutes to thicken into 'flax eggs'. Cook lentils in vegetable broth until tender but not mushy (about 20-25 minutes). Drain off any remaining liquid immediately and set the lentils aside.
- Heat olive oil in a pan over medium heat. Sauté onion, carrots, and celery until softened (about 8 minutes). Add garlic, tomato paste, thyme, and sage; cook for 1 minute until fragrant.
- In a large mixing bowl, combine the cooked, drained lentils, sautéed vegetables, chopped walnuts, rolled oats, flax eggs, soy sauce, and Marmite. Mix thoroughly until just combined. Taste and adjust salt and pepper as needed.
- Preheat oven to 375°F (190°C). Press the lentil mixture firmly and evenly into a lightly greased 9x5 inch loaf pan.
- Prepare the glaze by whisking together the ketchup, maple syrup, apple cider vinegar, smoked paprika, and Dijon mustard until smooth.
- Bake the loaf for 35 minutes. Remove from the oven and brush half of the prepared glaze evenly over the top surface.
- Return the loaf to the oven and bake for an additional 20–25 minutes, or until the glaze is sticky, dark, and slightly caramelized. Let the loaf rest in the pan for 10 minutes before slicing carefully.