Gather all ingredients.

Place potatoes in a pot, cover with cold water, and bring to a boil over medium-high heat. Turn the heat to medium-low, and boil potatoes until tender, about 25 minutes; drain.

Stir vegan mayonnaise, soy milk, olive oil, vegan cream cheese, and salt into potatoes, and mash with a potato masher until smooth and fluffy. Set mashed potatoes aside.

Preheat the oven to 400 degrees F (200 degrees C), and spray a 2-quart baking dish with cooking spray.

Heat vegetable oil in a large skillet over medium heat. Add onion, carrots, celery, frozen peas, and tomato; cook and stir until softened, about 10 minutes. Stir in Italian seasoning, garlic, and pepper.

Reduce heat to medium-low and crumble plant-based ground beef into the skillet with vegetables. Cook and stir, breaking up the meat substitute, until the mixture is hot, about 5 minutes.

Spread vegetarian meat substitute mixture into the bottom of the baking dish.

Top with prepared mashed potatoes, smoothing them into an even layer. Sprinkle potatoes with shredded soy cheese.

Bake in the preheated oven until the cheese is melted and slightly browned and the casserole is hot, about 20 minutes.

Enjoy!