Preheat the oven to 350°F (175°C). This ensures that the cobbler bakes evenly.

In a large mixing bowl, combine the sliced pears, granulated sugar, lemon juice, cinnamon, vanilla extract, and cornstarch. Toss gently until the pears are evenly coated. The cornstarch will help thicken the juices released by the pears during baking.

Transfer the pear mixture into a greased 9x13 inch baking dish, spreading it out evenly.

In another mixing bowl, whisk together the flour, baking powder, sugar, and salt until well combined. This ensures even distribution of the leavening agent.

Add the cold, cubed butter to the flour mixture. Using a pastry cutter or your fingers, work the butter into the flour until the mixture resembles coarse crumbs. This step is crucial for a flaky topping.

Pour in the milk and vanilla extract, stirring gently until just combined. Be careful not to overmix, as this can lead to a tough cobbler.

Drop spoonfuls of the cobbler batter over the pear filling, covering as much of the filling as possible. The batter will spread while baking.

Place the baking dish in the preheated oven and bake for 35-40 minutes, or until the topping is golden brown and a toothpick inserted into the topping comes out clean.

Once baked, remove the cobbler from the oven and let it cool for about 10 minutes before serving. This allows the filling to set slightly.