Mix peaches, sugar, bourbon, vinegar, and cornstarch in a bowl. Let marinade for 20 minutes.
Add butter to the bottom of a 9×13 baking dish and set in the oven to melt, about 10 minutes then remove.
In a medium bowl whisk together flour, baking powder, and salt. Add vanilla, bourbon, and milk and whisk until just combined.
Add the batter and spread out slightly, careful not to mix in with the melted butter. Note: The batter is thick, do not worry about creating an even layer of batter in the bottom of the pan as it will not spread out easily.
Top with the peach mixture and spread peaches in an even layer.
Bake for 45 minutes or until the edges are bubbly. Let cool for at least 15 minutes before serving.