Rinse the beans and dry them well. Trim the stem ends if they are not already trimmed. Dry beans brown better, so I never skip patting them with a towel.
Place your extra large skillet over medium heat. Let it warm up for a minute or two. A properly heated pan helps the beans start browning as soon as they land.
Add the oil first, then the butter. Let the butter melt and start to foam gently. The oil protects the butter, so it can turn golden instead of scorching.
Tip in all the green beans and sprinkle on the salt. Add the Italian herb blend now if you are using it. Give everything a quick toss so the beans are glossy and coated.
Set the lid on the pan, leaving a small gap for steam to escape. Turn the beans every 5 to 7 minutes with tongs. This keeps them cooking evenly and soaking up that buttery flavor.
If the beans start browning before the 15-minute mark, lower the heat to medium-low. The butter should turn nutty, not dark. A deep toasty smell is your best sign you are on track.
Keep cooking for about 25 minutes in total. The beans should still look green, but wilted and charred in spots. I sometimes leave them a few minutes longer for extra char.
During the last few minutes, stir in the parsley or capers if you like them. Taste a bean and adjust the salt. Right before serving, shower on the Parmesan and lemon zest.
Move the beans to a warm platter and serve while they are hot. They taste best fresh from the pan. Spoon any buttery bits from the skillet over the top.