First, preheat your oven to 375ºF (190ºC).
Prepare the fruit filling: Place the frozen fruit, lemon juice, cornstarch and sugar in a 9-by-13-inch (23-by-33-cm) baking dish and mix well with your hands to combine.
Make the cobbler topping: Place cornmeal, flour, sugar, baking powder and salt in a large bowl and whisk well to combine. Stir in the half-and-half and melted butter.
Evenly pour the batter over the fruit.
Bake the cobbler until the topping is dark golden brown and the fruit is bubbling, about 40-45 minutes.
Let the cobbler sit for at least 15 minutes before serving to allow the juices to settle. Serve warm or at room temperature with vanilla ice cream.