Melt the butter: Place the butter in a 13x9-inch baking dish. Put it in the oven for about 3 to 5 minutes, or until the butter is melted.
Mix the batter: In a large mixing bowl, whisk together the flour, granulated sugar, baking powder, and salt. Stir in the milk and vanilla extract until the batter is smooth.
Layer the cobbler: Carefully remove the hot dish from the oven. Pour the batter over the melted butter - do not stir.
Add toppings: Sprinkle the chopped pecans, brown sugar, and toffee bits evenly over the batter. Slowly pour the boiling water over everything—again, do not stir.
Bake for 30 to 35 minutes, or until the top is golden brown.
Cool on a wire rack for 30 minutes. The cobbler will thicken as it cools.
Serve warm, topped with vanilla ice cream if desired.
Notes
Cover and store in the refrigerator for up to four days. Reheat in the microwave or oven until warm.
Do not stir the layers before baking.
Cool for at least 30 minutes to allow the cobbler to set.