Scrub the sweet potatoes under cold water to remove any dirt or debris. Peel and cut them into approximately 1-2 inch cubes. Place the sweet potatoes in a large pot and cover them with cold water. Add a good amount of salt to the water and bring it to a boil.

Once boiling, lower the heat and let the potatoes simmer uncovered until you can easily slide a fork in and out of them, about 8-12 minutes.

While the sweet potatoes cook, brown the butter. Add the butter to a small saucepan over medium heat. Melt the butter stirring frequently. Continue to cook the butter until brown bits form at the bottom of the pan. It will take about 6-8 minutes. Once the butter is brown remove it from the heat.

Once the sweet potatoes are tender, drain them. Over low heat, add in the brown butter, milk, maple syrup, cinnamon, and rosemary to the sweet potatoes. Season with salt and pepper and use a potato masher to mash them until your desired consistency is reached. Taste for seasoning and adjust as needed. Add additional milk for a creamier mashed sweet potato. Garnish with the chopped pecans and additional brown butter and rosemary if desired.