Make your rosemary simple syrup first! In a small pan over medium, add the water and sugar. Stir to dissolve over the heat. Once dissolved, add the rosemary and simmer for 3-5 minutes. Turn off the heat and let it cool.
Make your charred lemon juice! Heat a cast iron pan over high heat and add the oil. Once the pan starts to smoke, add your lemons, cut side down. Check the lemons after 5 minutes and rotate around the pan if necessary. They should have a deep brown crust and be dripping with caramelized juice! Cool, juice, and strain.
Assemble! In a large bowl, add 10 ounces charred lemon juice, 15 ounces Becherovka, 10 ounces gin, and 5 ounces rosemary simple syrup. Stir and transfer to a pitcher with a pour spout. Place a sprig of rosemary in each bottle and (if you have it) set a funnel in the bottle. Pour to the top and repeat with all bottles.
Seal and label! Each bottle contains about 2 servings (4 ounces each). On a small card, write these instructions, 'Fill a rocks glass with ice. Pour 4 ounces of Gin + Tonic. Top with Tonic Water and Stir.' Tell your giftee to store it in the fridge and enjoy within 3-5 days. Cheers!
