Preheat the oven to 450°F.
Spread the lemon slices in a cast iron skillet
Spread the sliced onions on top of the lemon.
Sprinkle 1 tablespoon of the minced garlic over.
Lay down sprigs of sage and thyme, and give a sprinkling of oregano over everything.
Place the thyme, fennel seeds, oregano, 1 tablespoon of salt, and 1 teaspoon ground pepper in a mini food processor and process until ground.
Pour the oil into a small glass measuring cup, add 1 tablespoon of minced garlic, and the herb mixture, stir to mix and set aside.
Place the butterflied chicken breast side down and brush with the herb oil.
Flip the chicken over, pat dry with a paper towel and lift the skin off the breast. Brush with the herb oil on the skin as well as under it.
Place the skillet in the oven and bake for 30 minutes.
Pour the wine/champagne around the chicken and bake for another 30 minutes.
Remove from the oven, pour the lemon juice over the chicken and set aside to rest for 10 minutes.
Serve the chicken with the pan juices.