Lentil Walnut Loaf

Name: Lentil Walnut Loaf
Ingredients: 1 1/2 cups walnuts, toasted; 1 cup green or brown lentils, dry; 2 cups vegetable broth, plus more as needed; 1 tablespoon olive oil; 2 cups diced white or yellow onion; 1 cup diced celery; 1/2 cup diced carrot; 3 cloves garlic, minced; 1 teaspoon thyme, dried; 1/2 teaspoon sage, rubbed; 1 teaspoon rosemary, dried and crushed; 1/2 teaspoon salt; black pepper; 1 1/4 cups breadcrumbs; 1/4 cup tomato paste; 1 tablespoon flax meal, mixed with 2 tablespoons warm water; 1/4 cup ketchup, for glazing (optional)