First, clarify the butter so that you can fry the onions at high heat and put a very dark, almost burnt crust on them. Heat the butter in a small skillet over medium-high heat until it foams and browns. Remove from the heat. Tilt the skillet and carefully spoon off the foam, saving it in a small bowl. Pour the clear butter into another bowl, and pour the dark dregs at the bottom of the skillet into the bowl with the foam. Add the clear butter to a larger heavy skillet. (Discard the butter foam and dregs.)
Heat the skillet over medium-high heat. Add the onions, 3/4 teaspoon salt and 1/4 teaspoon pepper. Fry the onions, flipping them now and then, until they're dark on the edges, even black and crispy in spots, about 10 minutes. Add the honey and garlic and cook for 1 more minute. Add the vermouth, bring to a simmer and cook until the liquid thickens, about 3 minutes. Remove from the heat and let cool.
Put the sour cream and cream cheese in a mixing bowl and mix with a rubber spatula until smooth. Finely chop the fried onions on a cutting board and add them, along with their pan juices, to the cream cheese mixture. Stir in the chives. Add the cayenne and season with salt.
Transfer to a small bowl and garnish with more chives. (This can be made ahead of time and refrigerated.)
Recipe courtesy of Amy Thielen, reprinted from The New Midwestern Table. Copyright 2013 by Amy Thielen. Photographs 2013 by Jennifer May. Published by Clarkson Potter, a division of Random House LLC.