Peach Cake with Brown Sugar Icing

1 yellow cake mix
4-6 fresh peaches, or 16 oz. frozen peaches, unthawed, not canned, chopped
2, 3 oz. pkgs peach jello
4 eggs
1 c. oil
1 t. vanilla
Icing:
2 c. brown sugar
2/3 c. heavy cream
1 stick butter, room temperature
1 t. vanilla

Preheat oven to 350. Spray 9x13 dish. Beat together cake mix, dry jello, eggs, oil, and vanilla. just until incorporated, then fold in peaches. Pour batter into dish. Bake 40-45 minutes. Remove from oven and cool completely. While cake cools, combine brown sugar, cream, and butter in large saucepan over medium high heat. Bring mixture to a boil and cook for 2 minutes. Remove from heat and add vanilla. Once cooled, beat frosting 4-5 minutes, or until thickened, but still fluffy. Spread over cooled cake.