Start with the chicken:
Preheat the oven to 500°F with rack in upper third, or set to broil.
Mince and mash garlic to a paste with 1/2 teaspoon salt, 1 tbs olive oil and 1 tsp harissa (optional), then transfer to a bowl. Pat the chicken breasts dry and add to the bowl, coat with the garlic mixture. Generously crack black pepper on top, turning the breast over to make sure you cover both sides with the seasoning. Place in a foil-lined large shallow baking dish, and sprinkle 1/2 tsp brown sugar on top.
Roast for 10 minutes, skin side up, in the upper portion of the oven to brown the skin. When browned, move to the lower third of the oven and continue to cook for 10 – 15 minutes.
Remove from oven. Slice into the breast to check the doneness, the meat should no longer be pink; or, use a meat thermometer to confirm the chicken is heated through to 165 degrees F. Let sit on the countertop to cool for 10 minutes before slicing into 1/2″ thick pieces. You should have 4-6 pieces.
Then, the squash:
Pre-heat oven to 400 degrees. Add large baking sheet to the oven to heat up.
Cut the squash in half from the stem to the navel. Using a large metal spoon, scoop out the stringy interior and the seeds. Slice squash into 2″ half moon slices. You should have about 6 slices.
In a mixing bowl, add 1 tsp sweet paprika, 4 tbs olive oil and a squeeze of half a lemon. Stir to combine, add squash slices and toss in the oil mixture until they are evenly coated. Sprinkle with 1 tsp Maldon Salt, cracked pepper and 1 tsp brown sugar.
Place half moon squash pieces on the sheet, flat side down. Add to the squash to the oven and cook for 15-20 minutes. Remove from oven when a knife slips easily through the flesh and the tops of the squash is caramelized. If you want to achieve a more golden surface, broil the squash at the last minute quickly, but keep a eye on it to make sure it doesn’t burn.
Remove from oven.
Remove parsley, tarragon and chervil leaves from stems. Chop all your herbs finely (including the chives). In a small dish, combine honey and vinegar, and whisk to dissolve the honey. Add olive oil in a slow stream and whisk to emulsify.
On a large platter, arrange squash and chicken slices and sprinkle sumac over the chicken. Drizzle dressing over the whole dish and toss your herbs on top. Serve.