• Set oven. Preheat the oven to 300°F, and adjust a rack to the center.

Prep Onions

• Leaving the skin on, wash and dry the onions. Then, with the skin still on, cut the root end off of each one, just about ½-inch, only enough to create a base so the onions don’t roll. Then, slice about 1-inch off the tip (top) end of each one, and use the knife to mark an “X” on the surface, only cutting into it about ½-inch or so.

  Place them in a 9 x 13 x 2-inch pan, on their bases.
• Drizzle about 3 tablespoons of the olive oil on the flat surface of the onions -- over the "X." Sprinkle generously with salt and pepper.

Roast the Onions

• Place in the preheated 300°F oven, uncovered.
• After 1 hour, remove them from the oven and drizzle with the remaining 2 tablespoons of oil, making sure it seeps into the "X." Now cover the pan lightly with foil and return them to the oven for 1 more hour.
• Remove the onions from the oven again and take off the foil. Add about half of the fresh herb sprigs to the pan, surrounding, and on top of the onions. Evenly distribute the butter among the onions, on the top center of each one.

  Uncovered, return the onions to oven and roast for another 30 minutes.
• Baste the onions with the juices from the bottom of the pan and turn the heat up to 350°F.

  Still uncovered, continue to roast for 1 to 2 more hours, basting them every 20 minutes with more juices from the bottom of the pan. (It's your call -- the longer you roast them, the more caramelized and soft they'll be.)

  And for an even deeper flavor, when you turn the oven up to 350°F, peel and cut the onions into quarters from the "X" at the top, before continuing to roast them.
• Cool and serve. Remove from the oven and let them cool in the pan. If you haven’t already done so, when they’re cool enough to touch, take off the skins and slice. Serve with the remaining fresh herbs.