Preheat oven to 350 degrees. Spray the 12 cups of a standard muffin tin with non-stick cooking spray.
Place 1 piece of butter into each prepared muffin cup. Sprinkle 1 tsp brown sugar on top of each piece of butter. Sprinkle with ground cinnamon on top.
Place into oven for 5 minutes until butter has melted.
Take a paring knife and cut one peach in half from stem all along the peach pit to the other side, literally cutting peach in half. Give it a twist to make 2 halves. Take a spoon and pop out the pit.
Lay both halves of peach on cutting board and slice very thinly.
Place 3 slices of thinly cut peaches into each muffin tin cup on top of the melted butter/brown sugar in a fan shape.
In a large mixing bowl beat together cake mix, eggs, milk, melted butter, and a pinch of cinnamon until well combined. Dice up one peach and fold into mixture.
Using a small scoop place mixture on top of the peaches in the muffin tin cups. Don't over fill.
Bake in preheated oven for 15-18 minutes or until toothpick inserted comes out clean. Let cool for 5 minutes before taking a knife and go along the outside of cakes to loosed them up. Then take a spoon and insert to the bottom and pop the cakes out and place peach side up on a wire rack. Serve with ice cream.