Creating the perfect Blueberry and Nectarine Cobbler is easy if you follow these steps:

1. Preheat Oven: Begin by preheating your oven to 350°F (175°C).
2. Prepare Fruit Filling: In a large bowl, combine the blueberries and sliced nectarines. Add the sugar, lemon juice, cornstarch, vanilla extract, and ground cinnamon. Toss gently to coat the fruit evenly. Pour the fruit mixture into a greased 9×13-inch baking dish.
3. Mix Dry Ingredients: In another bowl, whisk together the flour, baking powder, and salt until well combined.
4. Combine Wet Ingredients: In a separate bowl, mix the melted butter and milk until combined.
5. Combine Mixtures: Gradually add the wet ingredients to the dry ingredients, stirring until just combined. The batter will be slightly lumpy, which is perfectly fine.
6. Spread Batter: Pour the batter evenly over the fruit mixture in the baking dish. Do not stir; the batter will rise and create a topping as it bakes.
7. Bake: Place the baking dish in the preheated oven and bake for 30-35 minutes, or until the cobbler is golden brown and the fruit is bubbling.
8. Cool: Once baked, remove the cobbler from the oven and let it cool for about 10-15 minutes before serving. This allows the juices to set slightly.
9. Serve: Scoop out portions and serve warm, optionally topped with a scoop of vanilla ice cream.

These simple yet effective steps will help you create a delicious Blueberry and Nectarine Cobbler that your family and friends will love!