Preheat oven to 500F.
Heat a small skillet over medium heat and melt butter. Add garlic and stir 2 minutes. Add breadcrumbs and toast to golden. Remove from heat and let cool in the bowl of a food processor.
Once cool, add hazelnuts and pulse to finely chop nuts and combine with breadcrumbs. Add cress or arugula and season with nutmeg. Add Parm, thyme, lemon zest and about 1/3 cup EVOO to food processor (count to 6 while pouring it in a slow stream).
Meanwhile, heat a cast-iron skillet or other large, heavy, oven-proof pan over medium-high heat.
Loosen skin of the chicken over breast meat, thighs and legs, and stuff with the breadcrumb mixture -- be careful not to rip the skin. Season the chicken liberally on both sides with salt and pepper.
When cast iron pan is hot and water splashed on surface dances, add a couple tablespoons EVOO, 2 turns of the pan. When oil smokes, about 30 seconds, add chicken, skin side down and weigh it down with the brick or another heavy pan weighted with dry beans. Brown 5-6 minutes then transfer to oven and roast 12-15 minutes. Flip chicken and roast 20 minutes more, uncovered and skin-side up. Remove from oven and let stand 10 minutes, douse with lemon juice. Carve and serve alone with crusty bread or with Rice Pilaf and Roasted Onions.
Serve with Roasted Onions and Rice Pilaf alongside.