In a medium sauté pan, over a medium-high heat, melt butter. Continue to let the butter cook until it starts to brown, swirling the pan as it cooks. Once the butter is brown and smells nutty, (but NOT burnt) add onions and salt. Toss in the butter and cook until they are caramelized, and even a little charred on the edges, about 10-12 minutes. Stir occasionally.
Once the onions are cooked, add the garlic, red pepper flake and honey. Cook another minute or so. Add the sherry, and cook until almost all the liquid has evaporated. Let cool.
In a small bowl mix greek yogurt and cream cheese until smooth. IMPORTANT! Make sure the onions and garlic are cool before adding into the greek yogurt and cream cheese, otherwise it will be runny! Add cooled onion mixture along with any juices that have accumulated and chives. Mix until combined. Season with salt and pepper. Sprinkle with chives if desired. Serve chilled or at room temperature.