Step 1

Arrange your oven rack to the bottom third of the oven and heat it to 425 degrees F. Set out a cast-iron skillet or small flat-bottomed roasting pan.

Step 2

Using a can opener, remove the label and top of a tall, thin can such as a can of green beans or tomato soup, saving the contents for a later use. Rinse the can and pour in the wine followed by the lemon zest and juice of half of the lemon. Add the rosemary sprigs. Smash, peel and roughly chop 2 of the garlic cloves and add to the can. Stand the can in the center of your skillet or roasting pan and, being careful of the sharp edge, fit the chicken cavity over the can so that it sits upright. Brush the chicken with the butter and season well with salt and pepper.

Step 3

Scatter the onions and remaining 2 unpeeled garlic cloves around the chicken and pour the chicken broth into the bottom of the pan.

Step 4

Carefully transfer to the oven and roast until the internal temperature of the thigh reaches 165 degrees F, about 1 hour and 15 minutes. If the onions start to go dry, add another splash of chicken broth to the pan.

Step 5

Carefully remove the chicken from the can and set aside on a cutting board to rest for 10 minutes while you make the pan sauce.

Step 6

Remove the rosemary from the can and pour the schmaltzy wine mixture into the pan. Bring to a simmer over medium-high heat, scraping the bottom of the pan to remove any stuck-on bits, and reduce by about half. Stir in the cream if using, as well as the mustard and spinach. Finish the sauce with the parsley and season to taste with salt and pepper and more lemon juice and zest as needed.

Step 7

Carve the chicken and serve either in the pan or with the sauce on the side.