In a large pot, add the potatoes, carrots, and chopped onion. Cover with water and bring to a boil.
Reduce heat and simmer for about 20-25 minutes, or until the vegetables are tender.
Drain the vegetables and return them to the pot.
Use a potato masher or fork to mash the vegetables to your desired consistency.
Stir in the butter until melted and well combined.
Gradually add the beef or vegetable broth, stirring until the mixture is smooth and creamy.
Season with salt, pepper, and dried thyme (if using).
Enjoy your meal!