These ingredients seem the right proportions. I think works better, as shown, rather than on the rocks, unlike how I prefer my negroni. Might even grow to prefer to Negroni as it invites more variations.
I just used to make an excellent White Lady. I used a bit more than the specified. From Simon’s comment below I assume the additional dry shake (without ice) helps the foaming? Will keep the bottle in the fridge to ensure effectiveness.