Preheat the oven to 400°F (200°C). Lightly oil a 9 x 13-inch baking dish.

Peel and cut 2 lb (900 g) russet potatoes into 1-inch pieces.

Boil the potato pieces in salted water until fork-tender, about 15 to 20 minutes. Drain the potatoes well.

Mash the drained potatoes with 1/2 cup (120 ml) unsweetened almond milk and 2 tbsp (28 g) vegan butter. Season the mash with salt and black pepper.

Dice the yellow onion, carrots, and celery. Mince the garlic.

Heat 2 tbsp (30 ml) olive oil in a large pan over medium heat. Sauté the onion, carrots, and celery until softened, about 7 to 8 minutes.

Stir in the minced garlic, 1 tsp dried thyme, and 1/2 tsp dried rosemary. Cook for 1 minute until fragrant.

Add 2 tbsp (32 g) tomato paste and cook for 1 minute. Stir in 1 1/2 cups (290 g) brown lentils, 2 cups (475 ml) vegetable broth, and 1 tbsp (15 ml) soy sauce.

Simmer the lentil filling until thick and saucy, about 10 to 15 minutes. Season with the remaining salt and black pepper.

Spread the lentil filling evenly in the prepared baking dish. Spoon the mashed potatoes over the filling and smooth the surface.

Bake until the potato topping is golden and the filling bubbles around the edges, about 20 to 25 minutes. Rest for 10 minutes before serving.

Sprinkle the pie with 2 tbsp (8 g) fresh parsley. Slice and serve warm.