Crush peppercorns with a mortar and pestle or the side of a chef’s knife. Remove zest from lime in wide strips with a vegetable peeler, leaving white pith behind. Place in a medium bowl. Add the lime’s juice, peppercorns, whole chiles de árbol, Torani syrup and salt. Cover and chill 8–12 hours. Strain mixture through a fine-mesh sieve into another medium bowl. To make 1 drink, mix ¼ cup syrup mix with ¾ cup club soda in an ice-filled glass. Garnish with a lime wedge and crushed chile de árbol.