Substitutes:

• Gin: Any kind of gin of your liking can be used to make this cocktail. If you're out of Gin, vodka can be a good substitute as it's neutral in flavor.
• Elderflower Liqueur: Saint Germain is the most famous elderflower liqueur on the market, but any other brand will work. If you can't find elderflower liqueur, an elderflower cordial or syrup can be used as a substitute; just make sure to adjust the quantities depending on the sweetness of the product you’re using as an alternative.
• Lemon Juice: Fresh is best, but bottled lemon juice can work if you're in a pinch. Just be aware it may alter the taste slightly. Another option would be to use freshly squeezed lime juice; it will work well in this recipe too.
• Egg white: Pasteurized eggs can be used instead of fresh eggs. If you don’t like using raw eggs at all in your cocktails, you can simply omit this step: your drink won’t have the same frothy texture as if using egg white, but it will taste equally delicious. If you want to make your cocktail foamy without using egg white, you can use ½ ounce of aquafaba (chickpeas water) as a substitute. Follow all the steps, as aquafaba also needs to be shaken twice to make a proper foam.
• Lavender Syrup: If you can’t find lavender syrup, you can use any kind of floral syrup of your liking (rose, orange blossom, hibiscus…). If you want to stick to lavender, you can also easily make your own syrup at home:
  • Ingredients: 
    • 1 cup sugar
    • ½ cup water 
    • 1 tablespoon dried lavender, tied in a cheesecloth or paper sachet
  • Bring the water to a boil. Add sugar and lavender and simmer for 10 minutes. Remove the lavender and allow the mixture to cool to room temperature. Strain into an airtight container and refrigerate. The syrup will keep for up to two weeks.

Making a Pitcher of Flower Power Sour:

• Scale: To make a pitcher that serves 8, multiply all the ingredients by 8. That would be 16 oz of Gin, 8 oz of lemon juice, 4 oz of elderflower liqueur and 4 oz of lavender
• Mix: In a large pitcher, combine the Gin, elderflower liqueur, lemon juice, and lavender Add ice and stir well.
• Serve: Strain to remove the ice, serve immediately into chilled coupe glasses and garnish each glass with a lavender sprig. If you have some leftovers, be sure to keep it in the fridge (make sure no ice cubes are left inside) in an airtight container.

Making it Non-Alcoholic:

• Gin Substitute: Use a non-alcoholic gin substitute; these are available and reasonably mimic Gin's botanicals.
• Elderflower Liqueur Substitute: Opt for an elderflower cordial or syrup instead of the liqueur. Elderflower juice or elderflower lemonade are also great alternatives.
• Proceed As Usual: Use these non-alcoholic substitutes instead of the regular ingredients, follow the original steps, and enjoy a non-alcoholic version.

Making it Vegan:

• Egg White Substitute: To make this cocktail vegan, omit the egg white or use a vegan alternative like aquafaba (the liquid from canned chickpeas). It froths up just like egg whites when shaken. Remember that it has to be shaken twice (once with ice cubes and once without) in order to get the proper consistency (see section above, “Substitutes”).