Place square piece of 1-inch square piece of kombu and 5 quarter-inch-thick celery slices in the bottom of a small pitcher. Pour in the sake and let the flavors come together for a few minutes, until it just begins to color. Strain the sake into a mixing glass filled halfway with ice. Add gin and bitters. Gently stir until well-chilled and diluted, about 20 seconds. Strain into a chilled cocktail glass. Garnish with a strip of kombu. This recipe is courtesy of Greg Henry for SippitySup.com.