Preheat oven to 375°F. Butter a 9x13 inch baking dish.

Pro tip: Place both ½ cup + 1 tablespoon butter for cobbler and ⅓ cup + 1 tablespoon butter for pecan topping in separate glass dishes in the preheating oven to melt with lovely brown bits.

In a large bowl, gently toss blackberries with both sugars, lemon juice, and cornstarch. Let macerate for 15-20 minutes while preparing other components.

Pour blackberry mixture into prepared baking dish and spread evenly.

In a large bowl, whisk together flour, brown sugar, granulated sugar, baking powder, and salt.

In a separate bowl, combine milk and vanilla. Add to dry ingredients and stir just until combined.

Stir in melted butter until just incorporated, then gradually add boiling water, stirring until smooth. Don't overmix.

Spoon batter evenly over the blackberry mixture, spreading gently to cover most of the fruit.

In a medium bowl, combine chopped pecans, flour, brown sugar, thyme, and salt.

Stir in melted butter until mixture is evenly moistened and holds together when pressed.

Sprinkle pecan mixture evenly over the cobbler batter.

Bake for 50-55 minutes, or until the pecan topping is golden brown and the cobbler layer is cooked through.

Optional broiling step: For extra caramelization, broil for 1-2 minutes in the last few minutes, watching closely.

Let cool for 10-15 minutes before serving, or store overnight uncovered.

Reheat uncovered at 300°F for 15-20 minutes until warmed through and pecan topping is re-crisped.

Serve warm with vanilla ice cream or lightly sweetened whipped cream.

Store overnight uncovered at room temperature.

Transport uncovered to maintain crispy topping.

Cobbler tastes even better the next day as flavors meld.