) Preheat the oven to 375°F.2
) Discard the giblets from the chicken cavity or save for another use.
Rinse the chicken well inside and out, and dry well with paper towels.
Drizzle a couple tablespoons of olive oil in the bottom of a roasting pan that’s just a bit larger than the chicken.
Scatter the onion slices in the pan, separating each slice into a few pieces.3
) Season the chicken cavity with salt and pepper, then stuff the whole herb sprigs into the cavity.
Set the chicken on the onions.
Drizzle the remaining olive oil over the bird and season generously with salt and pepper.4
) Roast the chicken until the skin is wonderfully amber-brown and juices from the cavity run clear when tipped (insert a long-handled fork, such as a carving fork, into the chicken and carefully lift to tip slightly, so the juices run into the roasting pan), about 1 1/2 to 1 3/4 hours.
When the onions begin to brown after about 45 minutes, pour 1/2 cup of the vermouth into the pan, adding 1/4 cup more later if needed.5
) Take the pan from the oven, scoop the herbs from the cavity into the pan and set the chicken aside on a carving board, covered loosely with foil to keep warm.
Meanwhile set the roasting pan on the stove over medium heat, add the remaining 1/2 cup vermouth and simmer to reduce slightly, 3 to 5 minutes, stirring gently to scrape up cooked bits from the bottom and sides of the pan.6
) To serve, carve the legs and breast meat from the chicken and arrange on individual plates.
Drizzle the cooking juices over, and spoon some of the cooked onions alongside.