Chill a cocktail glass thoroughly.
Add the gin and two dashes of peach bitters to a mixing glass.
Add the mint leaves and ice, then stir for 20 seconds — long enough to chill, short enough that the mint does not turn grassy.
Strain into the chilled glass.
Float two fresh mint leaves on the surface.
On the IBA official list as one of the Unforgettables. Not to be confused with the bourbon-and-grapefruit Brown Derby, which is a different drink entirely. With this little to hide behind, use a gin you would happily drink neat.
My Bar Shelf reads your shelf and shows you every cocktail you can make from what you already own, including Derby.