Gently peel your 12 hard-boiled eggs and set them aside.

In a medium saucepan, combine the sliced beets, sugar, vinegar, red onion, unsalted butter, salt, and black pepper. Heat over medium until the sugar dissolves, then simmer for 5 minutes.

Place the peeled eggs into a clean glass jar. Pour the hot beet brine over the eggs and refrigerate for at least 6 hours.

Once pickled, remove the eggs from the brine. Slice them in half and scoop out the yolks into a bowl, add a tablespoon of the brine and mash until smooth.

Spoon or pipe the yolk mixture back into the halved egg whites.

Sprinkle with freshly chopped chives and serve immediately.