For the strawberry rhubarb simple syrup:

1. In a medium pot, bring strawberries, rhubarb, sugar and water to a boil. Lower heat and let simmer, stirring occasionally, until fruit is broken down, about 20 minutes.
2. Remove from heat and let sit until cools to room temperature, about 60 minutes (or 30 minutes in the refrigerator!).
3. Place a cheese cloth or fine mesh strainer over a medium mixing bowl and pour strawberry rhubarb mixture into the cheese cloth or strainer. Use a wooden spoon to press down on the mixture to strain. Once you’ve extracted as much liquid as possible, store the remaining fruit pulp in the fridge for future use.
4. Using a funnel if needed (I use a glass measuring cup), transfer the simple syrup into a glass jar and store in the refrigerator for up to 3 weeks.

For the cocktail:

1. In a cocktail shaker, add gin, strawberry rhubarb simple syrup, lemon juice, mint, and egg white (or aquafaba) and shake vigorously for about 15 seconds.
2. Add ice to cocktail shaker and shake again until cold, about 30-60 seconds.
3. Strain drink into glass and fill to the top with soda water.
4. Optional: Garnish with rhubarb peel