For the pot roast:

Season the beef chuck roast with kosher salt and ground black pepper.

Heat the avocado or olive oil in a large Dutch oven or heavy-bottomed pot over medium-high heat.

Sear the beef on all sides until a nice brown crust forms, about 2-3 minutes per side.

Remove the beef from the pot and set aside.

Add the diced onion, carrots, celery, and minced garlic to the pot. Sauté for 5-7 minutes, until the vegetables are softened.

Sprinkle the tapioca flour or arrowroot starch over the vegetables and stir to coat.

Slowly pour in the beef broth, balsamic vinegar, and maple syrup, stirring constantly to prevent lumps.

Add the seared beef back to the pot, along with the fresh thyme and rosemary sprigs.

Bring the mixture to a boil, then reduce the heat to low, cover, and simmer for 2-3 hours, or until the beef is very tender.

For the mashed potatoes:

In a small saucepan, melt the butter over medium heat. Cook, stirring occasionally, until the butter turns golden brown and has a nutty aroma, about 5-7 minutes.

Add the smashed garlic cloves and cook for an additional 2 minutes.

In a large pot, cover the peeled and cubed potatoes with cold water. Bring to a boil and cook until the potatoes are tender, about 15-20 minutes.

Drain the potatoes and return them to the pot. Mash the potatoes with a potato masher or ricer.

Slowly pour in the browned butter and garlic mixture, the milk, and 2 teaspoons of kosher salt. Mash until smooth and creamy.

Season with additional salt and ground black pepper to taste.