Preheat the oven to 450ºF and set out a baking sheet or roasting pan.
If the chicken is not butterflied (also called “spatchcocked”), simply place it breast-side down on a work surface and, using kitchen shears, cut along both sides of the backbone in order to remove it. Discard the backbone, salt the cavity, and flip the chicken over. Firmly press down on the centre of the breastbone in order to flatten the chicken out. Set aside.
In a small bowl, mix together the butter, chopped tarragon and parsley, lemon zest, minced garlic, and a pinch of salt and pepper. Using a spoon, divide the butter under the skin of each half of the chicken. The spoon will help you get between the meat and the skin and allow you to infuse that lovely herby butter flavour throughout the whole roast.
In the bottom of the baking sheet or roasting pan, lay out the tarragon sprigs so that they will nestle under the chicken. Top those with the strips of bacon and scatter over the unpeeled garlic cloves. Place the chicken skin-side up on top of the bacon, tarragon, and garlic, and drizzle the skin with a little olive oil. Season with salt and pepper and roast in the preheated oven for 35 to 45 minutes or until the internal temperature of the thigh meat reaches 165ºF.
Remove the chicken from the oven and allow it to rest for 10 minutes before digging in.