Pour the gin into a large jar. Add the dried lavender, cover and shake to combine. Let sit at room temperature for 4 hours. Strain the gin and then store in a clean jar. This will make enough for about 15 cocktails.
For the Rhubarb Simple Syrup
Combine the chopped rhubarb, water and sugar in a pot. Bring to a boil and then reduce the heat to a low simmer. Cover and let simmer for 15 minutes. Turn off the heat and leat sit for another 15 minutes if desired. Strain through a fine mesh strainer, pressing the pulp to drain as much of the syrup as you can. Let cool and then store in the fridge until needed. This will make approximately 3 cups of syrups, enough for about 15 cocktails.
For the Rhubarb Lavender Gin Cocktail
In a cocktail shaker measure out the lavender infused gin, rhubarb simple syrup, fresh lemon juice and the egg whites. Add a generous scoop of ice then cover and shake. Shake for at least 20 seconds to make sure the egg white is sufficiently mixed in. Strain into a coupe glass and serve!