Peel the sweet potatoes and cut them into roughly 1-inch chunks so they cook evenly. Place them in a large pot and cover with cold water by about an inch. Add a generous pinch of salt.

Bring the pot to a boil over high heat, then reduce to a steady simmer. Cook for 15 to 18 minutes, until a fork slides into the largest piece with no resistance at all. You want them very tender, not just cooked through.

While the potatoes cook, make the brown butter. Place the butter in a small, light-colored saucepan over medium heat. Swirl the pan gently as it melts. After about 3 to 4 minutes you will hear the sputtering slow down and see golden-brown specks forming on the bottom of the pan. The smell will shift from butter to something toasty and nutty. Pull the pan off the heat immediately and pour the brown butter into a small bowl so it does not continue cooking.

Drain the sweet potatoes in a colander and let them sit for 1 full minute. You want the steam to escape so the mash does not end up watery. Shake the colander gently to help them dry out.

Return the drained sweet potatoes to the warm pot. Add the brown butter, warm heavy cream, cinnamon, salt, and pepper. Mash with a potato masher until smooth and creamy. For a silkier texture, use a hand mixer on low for about 30 seconds.

Taste and adjust. Add more salt if needed or a splash more cream if you want a looser texture. Transfer to a serving bowl and drizzle a little extra brown butter over the top if you have any left, or finish with a small pat of regular butter for the table.