Place stick of butter in a 9x13 baking pan. Place in the oven until butter is fully melted. Once melted, remove from the oven and toss pecans in the butter (they will remain on the bottom of the pan).
In a mixing bowl, combine the flour, Rivulet, white granulated sugar, whole milk, vanilla extract, and 1/2 c. of the brown sugar. Mix until fully-combined.
Pour batter over layer of butter + pecans. Don't mix.
Sprinkle the remaining 1 c. of brown sugar over the batter. Don't mix.
Pour the hot water on top of the cobbler. Don't mix.
Bake for roughly 45 minutes or until golden brown. Start watching it around the 35 minute mark!