Preheat your oven to 180°C (350°F) and lightly grease a 9x5 inch loaf pan with oil or non-stick spray.
Peel and finely chop the onion, then mince the garlic. Set aside.
Heat olive oil in a skillet over medium heat until shimmering, then add the chopped onion and minced garlic. Sauté for about 5 minutes, stirring occasionally, until the onions are translucent and fragrant.
Add the sliced mushrooms to the skillet. Cook for 8-10 minutes, stirring occasionally, until the mushrooms release their juices and turn a deep brown, filling your kitchen with a rich, earthy aroma.
While the mushroom mixture cools slightly, rinse the lentils and cook them in boiling water for 20-25 minutes until tender but still holding their shape. Drain and set aside.
In a mixing bowl, mash the cooked lentils lightly with a fork or potato masher, leaving some texture. Add the sautéed mushrooms, onion, garlic, breadcrumbs, beaten egg, tomato paste, thyme, sage, and smoked paprika. Mix everything thoroughly until well combined.
Season the mixture with salt and pepper to taste. The mixture should be sticky enough to hold together when pressed; add a splash of water or broth if it feels too dry, or more breadcrumbs if too wet.
Transfer the mixture into your prepared loaf pan and press down firmly with a spatula to ensure it’s compacted. Smooth out the top for an even surface.
Bake in the preheated oven for 45-50 minutes, until the top is golden brown and a little crispy. The loaf should feel firm and set when gently pressed.
Allow the loaf to rest in the pan for at least 10 minutes after baking. This helps it set and makes slicing easier.
Carefully run a serrated knife around the edges, then slice the loaf into thick pieces. Serve warm or at room temperature, enjoying the moist interior and crispy crust.
