Preheat oven to 350 degrees F. Spray 9x5-inch loaf pan with cooking spray and line with parchment paper.

Combine ground flaxseed or ground chia seeds and water in small bowl. Mix well. Let sit 15 minutes.

To medium saucepan over high heat, add 2-1/2 cups water and lentils and bring to boil. Cover saucepan and reduce heat to medium-low. Continue to cook 15-20 minutes until the lentils have softened. (Note: Alternatively, use instant pot. Pressure cook lentils with 2-1/2 cups water 8 minutes. Once cycle is complete, wait 10 minutes before releasing pressure.)

Drain cooked lentils through colander and set aside.

In large skillet over medium heat, heat oil. Add onions and garlic. Sauté 3-4 minutes until onions soften.

Add mushrooms, bell peppers, carrots, tomato sauce, salt and pepper. Cook until veggies have softened, 6-8 minutes.

To food processor, add lentils, veggies, flaxseed/chia mixture, bread crumbs, oats and thyme. Pulse 3-4 times until mixture starts to stick together. (Note: Batter should not be runny. If it is, add breadcrumbs to absorb moisture.)

Transfer batter to loaf pan. Press gently with spatula to flatten top and evenly distribute mixture.

Bake 40 minutes, until toothpick inserted in center comes out clean.

Let cool about 15 minutes before slicing.

Refrigerate up to 5 days or freeze for 1 month.

In saucepan over medium heat, heat oil. Add onions, garlic and mushrooms. Cook for 6-8 minutes, until mushrooms have softened.

Stir in tamari and sauté another 1-2 minutes.

Add nutritional yeast, tahini, pepper and vegetable broth. Cook, stirring, until well combined.

In small bowl, combine cornstarch and 2-3 tablespoons of mushroom sauce; mix until well combined.

Pour cornstarch mixture into saucepan and mix well. Cook, stirring occasionally, until mixture thickens.

Serve immediately. Refrigerate up to 5 days.