Adjust oven rack to middle position and preheat to 425°F.

Prick sweet potatoes with a fork, microwave until very soft, about 10-15 mins, flipping every 5 mins.

Slice potatoes to release steam; scoop out flesh and mash until smooth.

Discard skins.

Whisk together milk, melted butter, and eggs in a large bowl.

In another bowl, combine cornmeal, flour, brown sugar, baking powder, baking soda, and salt.

Stir sweet potato mixture into cornmeal mixture until well combined.

Heat 1 tbsp butter in a 10-inch oven-safe skillet over medium-high heat until bubbling, about 3 mins.

Swirl to coat skillet.

Pour batter into hot skillet, smooth top.

Bake until golden brown and toothpick inserted comes out clean, 25-30 mins.

Cool in skillet on wire rack for 1 hour.

Loosen edges with spatula, slide onto cutting board.

Cut into wedges and serve.