4 oz fresh grapefruit juice
1 oz gin, such as Knox Whiskey Works
3/4 oz St. Germain
1/2 oz simple syrup
4 oz chilled German- or Czech-style Pilsner
Fill a pint glass (or a large Collins glass) a little less than half-full with ice.
Fill a cocktail shaker half-full with ice. Add grapefruit juice, gin, liqueur, and simple syrup. Shake to chill and strain into glass. Top with cold beer and gently stir.