Place half of the cooked lentils in a large bowl. Place the remaining half of the lentils in the base of a food processor and pulse ~10 times to create a rough lentil paste. Add this to the large bowl.

Add in the walnuts to the food processor and pulse to create a finely chopped walnut. Add this to the large bowl.

Heat the olive oil in a large skillet over medium heat. Add the onion and cook until very soft, about 10 minutes. Add in the garlic, celery, carrots and mushrooms and cook another 10 minutes until the vegetables are very soft and almost caramelized.

Stir in the apple, thyme, oregano, sage, paprika and salt to the skillet and cook another minute or so, then add the entire mixture to the lentil bowl.

Preheat the oven to 350 degrees F. Grease a 9 inch loaf pan and line it with a piece of parchment paper for easy removal.

Stir in the flax seeds, balsamic vinegar, bread crumbs to the lentil mixture and stir to combine. Slowly add in the flour, ~1-2 tablespoons at a time until a mixture forms that isn't crumbly. It should easily hold together when pinched. Taste, adding salt/more seasonings/pepper as desired.

Press the lentil mixture into the loaf pan, pressing down the sides to even out. Whisk together the remaining glaze ingredients: ketchup, balsamic, maple. Taste, adding splashes of more vinegar/syrup as desired to create a tangy, sweet glaze as desired. Pour over the glaze, spreading in an even layer.

Bake for ~50 minutes until loaf if set. Remove and let cool for at least 15 minutes before removing and slicing. Allowing the loaf to cool slightly will make for easier slicing.