Put butter in a 13 by 9 by 2-inch baking dish and place in the oven to melt. Stir sugar and flour together and mix well. Slowly add milk and continue stirring to prevent the batter from lumping.
Being careful not to burn yourself, remove hot baking dish containing melted butter from oven; pour batter directly over butter in baking dish. Do not stir.
Spoon fruit on top of batter, then gently pour syrup on top. Do not stir. Sprinkle cinnamon on top of batter, if using. (*The most important part of this dish is not stirring the mixture at this point in the recipe.*)
Bake for 30 to 45 minutes or until golden brown. Your batter will rise above your fruit, producing the most wonderful of crusts. Serve warm with vanilla ice cream or fresh whipped cream.
If they are available, by all means use fresh peaches. In a saucepan, mix 2 cups fresh peach slices with one cup sugar and one cup water. Bring the mixture to a boil and then simmer for about 10 minutes. Stir often, making sure the sugar is completely dissolved. Substitute this for the canned peaches.