Melt 1 tablespoon butter in a skillet. Add the peaches and brown sugar. Cook over low heat until the peaches release their juices and the sugar melts. Strain the peaches from the syrup formed (keep the peach syrup to pour over the baked Peach Dutch Baby!)
Preheat oven to 425°F.
Mix the eggs, sugar, milk, flour and salt together in a blender (or in a bowl with a whisk). It will make a thin batter.
Put the cast iron skillet in the oven (make sure it is clean first, if you used it to cook the peaches). Once it is hot, add the remaining 4 tablespoons butter. Once the butter melts, remove the pan from the oven, add the batter, then spoon the peached over the batter and return the skillet to the oven. Bake for about 25-30 minutes or until golden brown and very puffy.
Remove from the oven, add the peaches, berries and whipped cream, then drizzle the peach syrup over the top. Serve with more cream and peach syrup!