Fizz á la Violette
1/ Flash BLEND first 6 ingredients without ice (to emulsify mix). Then pour contents of blender into shaker and SHAKE with ice. Strain into chilled glass (no ice in glass) and TOP with soda from siphon.

Alternatively: 2/ SHAKE first 6 ingredients with ice and strain back into shaker. DRY SHAKE (without ice) and strain into chilled glass (no ice). TOP with soda water from siphon.
[['4.5 cl', 'Portobello Old Tom gin'], ['0.75 cl', 'Crème de violette liqueur'], ['3 cl', 'Lemon juice (freshly squeezed)'], ['1.5 cl', 'Sugar syrup (65.0°brix, 2 sugar to 1 water rich syrup)'], ['3 cl', 'Single cream / half-and-half'], ['3 cl', 'Pasteurised egg white'], ['Top up with', 'Soda from siphon']]
[['4.5 cl', 'gin'], ['0.75 cl', 'crème de violette liqueur'], ['3 cl', 'lemon juice'], ['1.5 cl', 'sugar syrup'], ['3 cl', 'single cream / half-and-half'], ['3 cl', 'egg white'], ['Top up with', 'soda from siphon']]