For the batter: Microwave butter in 20 second intervals until melted; set aside. In a medium bowl, whisk together flour, sugar, baking powder and salt. In a large bowl, whisk the egg and milk until uniform. Sift about ½ of the dry ingredients mixture through a fine–mesh strainer over the milk mixture; whisk together until a few lumps remain. Sift remaining dry ingredients over the batter; whisk until a few lumps remain. Add the melted butter and whisk until smooth.
For the peaches: Halve and pit peaches. Slice peaches ½–inch thick; transfer to large mixing bowl. Add brown sugar, salt, cinnamon, and lemon juice to peaches; stir to coat peaches evenly. Let peaches sit at room temperature for 5 minutes.
Add butter to a 12–inch skillet over medium heat. When butter is melted and bubbling subsides, add the peach mixture to skillet, scraping out any accumulated juices and sugar. Cook, stirring frequently, until peaches soften but are still intact, about 5 minutes. Add bourbon; cook for 1 minute, stirring constantly. Transfer to small heat–proof bowl and set aside.
For the crêpes: Set a 12–inch non–stick skillet over medium–low heat for 3 minutes. Increase heat to medium; melt ½ tablespoon butter until bubbling subsides and butter begins to smell nutty, 2 minutes. Ladle ¼ cup batter in center of pan; lift pan off heat and tilt in circular motion to disperse batter over surface. Cook until bottom of crêpe is golden brown, about 2 minutes. Flip crêpe and cook until second side is spotty golden brown, about 1 minute. Crêpes can be served immediately, or stacked and covered with aluminum foil to keep warm. Continue cooking batter, adding more butter to the pan as needed.
To serve, working with one crêpe at a time, sprinkle 1 tablespoon brown sugar in a line across center of crêpe; roll crêpe into tube shape. Arrange 2 crêpes per plate; divide peaches evenly over crêpes.