In a large skillet, heat olive oil and sauté mushrooms until they release moisture and begin to brown.

Add onion, garlic, carrots, and celery. Sauté until soft and fragrant. Let cool slightly.

In a large bowl, combine sautéed veggies with ground beef, mashed potatoes, eggs, salt, and pepper. Mix until well combined.

Boil for three to four minutes, just until pliable. Drain and set aside on a flat surface or parchment paper to cool.

Cut the cassava lasagna noodles in half lengthwise to create narrower strips.

Preheat oven to 350 degrees Fahrenheit (175 degrees Celsius).

Lightly grease a large baking dish and spread a thin layer of spaghetti sauce on the bottom.

Take each noodle strip, place a scoop of meat mixture on one end, and roll it up tightly.

Place each roll in the baking dish, meat facing up.

Spoon more spaghetti sauce over the top of the rolled noodles to cover.

Cover the dish with foil and bake for one hour.

Remove from oven and let rest for 10 minutes.

Garnish with freshly chopped parsley and serve warm.