Preheat oven to 350 degrees. Line a muffin tin with parchment paper or muffin liners. Cut biscuits into 1/2-inch pieces.Combine sugar and cinnamon in a small bowl. In batches, place biscuit pieces in the cinnamon sugar and toss to coat. Transfer to prepared muffin tin. Sprinkle any remaining cinnamon sugar over biscuit pieces.Stir together melted butter and brown sugar and pour over muffins. Bake 12-15 minutes, until tops are golden and biscuit pieces are cooked through. Cool 2-3 minutes before removing from pan.
For the Icing
Whisk together the powdered sugar and milk until smooth. Drizzle over baked muffins.These are best when they're fresh from the oven and warm, but can easily be reheated!