Step 1
Instruct garlic, sugar, coriander seeds, 1 cup kosher salt, and eight cups water to a boil in a abundant saucepan, stirring to dissolve sugar and salt. Switch to a abundant bowl and add 1 cup ice. Let frigid. (It’s doubtless you’ll perchance well additionally additionally refrigerate or freeze brine if you happen to could well well be attempting to desire to streak things up.)
Step 2
While brine is cooling, bone rooster breasts, leaving leg and thigh quarters intact. Delivery up by slicing off flit pointers; discard. Space rooster, skin facet down, on a slicing board. Working with 1 rooster half at a time, perspective the blade of a skinny, engaging knife flush against breast bone and decrease along bone to separate the rib cage from flesh. The most attention-grabbing bones last must quiet be in the flit, thigh, and drumstick. Repeat on the completely different facet (assign bones for making your subsequent pot of inventory).
Step 3
Space rooster halves in cooled brine. Duvet tightly and take a seat again 12 hours.
Step 4
Switch rooster to a rimmed baking sheet or baking pan and pick off coriander seeds. Unfold harissa all the way by rooster. Duvet tightly and take a seat again no decrease than 1 hour and as much as 12 hours.
Step 5
Preheat oven to 400° (if you happen to have confidence a convection oven, flip the convection fan on). Heat schmaltz in a abundant cast-iron pan over medium. Carefully space rooster halves, skin facets down, in pan, making clear the final skin is in the chunky. Cook until skin darkens and begins to crisp, about 5 minutes. Switch skillet to oven and roast rooster until skin is intensely unlit and meat is bigger than halfway cooked by, 20–25 minutes.
Step 6
Remove skillet from oven and fastidiously flip rooster. Return to oven and roast, skin facet up, until an instantaneous-be taught thermometer inserted into the thickest share of thigh registers 165°, 8–12 minutes.
Step 7
Switch rooster to a abundant platter, inserting skin facet up. Drizzle most certainly the most schmaltz over rooster and help last schmaltz alongside.
