Preheat your oven to 350°F (175°C).
Wrap the sweet potatoes in aluminum foil and bake them for about 1 hour. Once done, allow them to cool a bit, peel them, and then add them to a bowl. Set aside.
In a saucepan, melt 1 stick of butter over medium heat. Continue cooking the butter until it turns golden brown, emitting a nutty aroma. Transfer the brown butter to a bowl to cool.
In a large mixing bowl, combine the flour, light brown sugar, baking powder, cinnamon, and nutmeg.
Add the whole milk to the dry ingredients and mix until just combined.
Incorporate the mashed sweet potatoes and cooled brown butter into the mixture, stirring until well combined and smooth.
Place 1 stick of butter in a 9x9-inch baking pan and put it in the oven until it melts. Remove from the oven.
Pour the sweet potato batter into the buttered pan. Spread it evenly.
Bake in the preheated oven at 350°F (175°C) for 20-25 minutes, or until the biscuits are golden brown and a toothpick inserted in the center comes out clean.
In a small bowl, mix the powdered sugar and milk until smooth and creamy.
Once the biscuits are done baking, let them cool slightly.
Pour the glaze over the top of the biscuits, spreading evenly.
