Pour the white wine into a 10-inch cast-iron skillet and set it aside.
Insert the lemon halves and garlic into the chicken cavity.
Tie the chicken’s legs together with kitchen string.
Slide the cold butter pieces under the skin of the chicken breasts.
Brush the chicken all over with Dijon mustard, then sprinkle it with salt and pepper.
Transfer the prepared chicken to the skillet with the white wine.
Roast the chicken in the preheated oven for 15 minutes.
After the initial 15 minutes, reduce the oven temperature to 350°F and continue roasting the chicken until an instant-read thermometer inserted into the thickest part of the thigh registers 170°F.
This should take approximately 1¼ to 1½ hours.
Remove the roasted chicken from the oven, cover it with a doubled sheet of foil, and let it rest for 15 minutes.
