Chill a Martini glass in the freezer for at least 30 minutes. Just before making the cocktail, remove the glass from the freezer. Moisten half the rim with ramp brine and roll in ramp salt.
Fill a mixing glass with ice and add the gin, mezcal and ramp brine. Stir for a minute to chill thoroughly. Place 1 king ice cube in the chilled glass and strain the cocktail on top. Garnish with the pickled ramp and serve immediately.