Preheat the oven to 450 degrees.
Sprinkle the chicken leg generously with salt and pepper.
In a small bowl, stir together the chopped garlic, parsley, and lemon confit to form the gremolata. Add oil from the jar of lemon confit if needed to form a paste. Use your finger to loosen the skin over the chicken thigh and drumstick, then pack the gremolata inside, reserving a tablespoon or so to rub on the outside of the skin.
Scatter the sunchokes and sliced garlic in a small cast-iron skillet. Drizzle with the olive oil, season with salt and pepper, and toss to thoroughly coat with the oil. Push to the edges of the pan and put the chicken in the middle.
Roast the chicken until the skin is browned and crisp and an instant-read thermometer inserted into the thickest part of the thigh reads at least 165 degrees, 20-30 minutes. Baste it with the oil in the pan a time or two during roasting, if desired. Remove from the oven, and let the chicken and sunchokes rest for a few minutes in the pan.
Transfer the chicken and sunchokes to the dinner plate, squeeze the lemon half over the chicken, and eat.