Add 1 ½ cups of lentils, 1 bay leaf, and 4 ½ cups of water to a medium pot. Bring the ingredients to a simmer and cover the pot. Cook the lentils for 20-25 minutes, until the water is absorbed, the lentils are tender, and they start to break down.
In a small bowl, combine 2 tablespoons of ground flaxseeds (flaxseed meal) with 4 tablespoons of water. Set aside.
Heat a skillet (frying pan) over medium-high heat, then add the onions, carrots, and celery. Cook the vegetables for 5-8 minutes, stirring often, until they start to soften. Add a tablespoon of water if the veggies begin to stick.
Stir in the chopped mushrooms and garlic. Continue cooking until the mushrooms soften and release any excess moisture.
Add the spices (thyme, oregano, basil, salt, and pepper) and the nutritional yeast. Mix well. Then stir in the tomato paste, tamari (or soy sauce), vegan Worcestershire sauce, maple syrup, and apple cider vinegar.
When the lentils and veggies are done, remove them from the heat and set them aside.
Preheat your oven to 400° F (200° C).
Add the oats to a food processor and blend for a minute or so until they break down.
Remove the bay leaf from the lentils and reserve 1 cup of the cooked lentils.
Add the remaining lentils, cooked vegetables, chopped walnuts, and flax seeds. Pulse a few times, leaving some texture from the vegetables and lentils.
Stir in the remaining 1 cup of lentils. Test the mixture by forming a ball. If it crumbles, the mixture is too dry. Knead it by hand for a few minutes to help the lentils break down and the oats to moisten. If the ball collapses, it’s too wet. In this case, I recommend adding more ground oats.
Line a small baking dish (mine is 10 inches x 7 inches) with parchment paper. Press the lentil mixture into the dish, spreading it evenly over the top.
To make the glaze, in a small bowl, combine 2 tablespoons of balsamic vinegar, 2 tablespoons of tomato paste, and 1 ½ tablespoons of maple syrup.
Spread the glaze evenly over the top of the loaf, cover the dish with foil, and place it in the center of the oven. Bake for 30 minutes, then uncover it and bake for an additional 10 minutes. The loaf should be firm in the middle.
If desired, test the loaf by inserting a toothpick into the center. It should come out clean.
After removing it from the oven, let the loaf rest for 15 minutes. Then use the parchment paper overhang to gently lift the loaf out of the baking dish.