2⁄5 jig Gin, Beefeater
1⁄5 jig Brandy (Bonded brandy like Christian Brother's Sacred Bond works well.)
1⁄5 jig Sweet vermouth, Martini & Rossi
Instructions
Stir well with ice, strain into cocktail glass.
Notes
In Straub's recipe, each component is given as 1/5 or 2/5 jigger, implying that a jigger is equal to the full drink. If it is indeed meant as a shot, and a jigger is understood as 1.5 oz., the ratios work, but as a standard 3 oz cocktail, adjustment to the ratio may be desirable. Jack Grohusko's specification of M&R vermouth and Gordon Dry Gin probably has more to do with sponsorship or marketing than design.
So I know we usually don't do drinks with odd measurements like parts and jiggers, but turning 2/5 of a 1 1/2 oz drink into ounces gets silly real quick - 3/5 and 3/10 of an ounce is hard to measure. The OP asked how I'd scale it up to a 3-4 ounce drink, and my best guess would be to swap the vermouth and gin amounts, so: 1.25 vermouth, and a fat 1/2 oz of gin, brandy and Angostura. Thanks, Zachary