Place some ice in a highball glass.
In a cocktail shaker, muddle the basil leaves, orange slice, Szechuan peppers, and sugar together until the basil is very aromatic and slightly bruised looking and the sugar is mostly dissolved.
Add the shrub and gin and top with ice.
Shake well, until the shaker is very cold and is sweating.
Strain into the prepared glass, top with club soda and garnish. You can garnish with an orange wedge or slice, basil leaves, and edible flowers if desired.