Stir Skrewball, coconut rum, and lime shrub over ice. Strain into a lowball glass with ice, and top with tamarind soda. Garnish with a spring of Thai basil, a lime wedge, and/or an edible flower.
The goal is to reach a balance of sweet, savory, sour, and herbal, so that no single note stands out too much.
For specifics on making the shrub:
I started with making a 1:1 water and brown sugar syrup, simmered the lime leaf and Thai
basil, and removed the leaves once they started looking pale. I juiced limes to get an 1 part of lime juice to add, added some of the lime peels to the simmer, and removed them once they looked pale. I added 1 part apple cider vinegar, and continued to simmer - I feel like going higher temp at this point evened out the vinegar taste after awhile. I poured everything into a jar, and added a second batch of lime leaf and Thai basil to steep while warm, then removed it once the jar had cooled entirely. Once cold, I added a single lime leaf to steep cold overnight, and obtained the herbal flavor I was looking for.
For 1 cup brown sugar syrup, 1 cup apple cider vinegar, and 1 cup lime juice - I used 16
lime leaves and 25 Thai basil leaves in simmering the brown sugar syrup, simmered 12 lime halves after adding the lime juice, and steeped another 16 lime leaves and 25 Thai basil leaves after adding the shrub to a jar and while it was still warm.
For a pared down spec in consideration of ingredient availability, and access to an Asian market and tamarind soda: