01 - Preheat oven to 375°F and line a 9x5 inch loaf pan with parchment paper.
02 - Heat olive oil in a large skillet over medium heat, then add onion, leek, carrots, and parsnips; cook for 8 minutes until softened.
03 - Incorporate garlic, mushrooms, and butternut squash; cook for 5 more minutes, stirring occasionally.
04 - Stir in baby spinach, tomato paste, thyme, sage, smoked paprika, salt, and pepper; cook until spinach wilts, then remove from heat.
05 - Combine ground flaxseed with water in a small bowl; let rest for 5 minutes to thicken.
06 - In a large bowl, combine lentils, sautéed vegetables, oats, breadcrumbs, flax egg, and parsley; mix thoroughly and adjust seasoning as needed.
07 - Press mixture firmly into the prepared loaf pan and smooth the surface.
08 - Mix maple syrup, balsamic vinegar, and tomato paste; brush evenly over the loaf top.
09 - Bake for 45 to 55 minutes until firm and golden; cool in pan for 10 to 15 minutes.
10 - Lift using parchment paper, slice, and serve.