Coconut-Corn Ice Cream with Brown-Sugar Syrup and Peanuts

Toast coriander seeds in a small dry skillet over medium heat, stirring often, until fragrant, 1-2 minutes. Transfer to a cutting board; crush with the bottom of a small pan or with a mortar and pestle.
Stir sugar and 1/3 cup water in a small saucepan over medium-low heat until sugar dissolves. Add coriander and peppercorns; season with salt. Bring to a simmer over medium heat. Simmer, swirling pan occasionally and brushing down sides with a wet pastry brush, until slightly thickened, about 5 minutes. Let cool. Strain; cover and chill for up to 1 month.
Using the large holes on a box grater, coarsely grate corn kernels from cobs into a large bowl; reserve cobs. Heat coconut milk in a large saucepan over medium heat until almost simmering. Add grated corn, corn cobs, and condensed milk; cook, stirring occasionally, until mixture barely begins to simmer, about 5 minutes. Remove from heat, cover, and let steep for 1 hour. Discard cobs.
Strain corn mixture through a fine-mesh sieve into a medium bowl, pressing on solids to extract as much liquid as possible; discard solids. Whisk in salt. Cover corn ice cream base; chill for at least 4 hours or overnight.
Process ice cream base in an ice cream maker according to manufacturer's instructions. Transfer to an airtight container, cover, and freeze for at least 3 hours and up to 1 week.
Scoop ice cream into bowls. Drizzle some brown-sugar syrup over. Garnish with peanuts and lime zest.