Preheat oven to 275. Core the onion: Using a sharp paring knife, core the center of your onion to create a hollow well. Make sure to not go all the way through the other side or else your butter will leak and it won’t be as good.
Stuff with butter: take 1 tbsp of softened butter and stuff it into the cavity of the onion, filling the hole all the way to the top. Add onion to cocotte.
Make the seasoned butter: Melt the remaining 2 tbsp of butter. Stir in the seasonings, then pour the melted butter into the well in the center of the onion, allowing it to overflow into the mini.
Bake for about an hour, or until the onion is super soft and the layers peel easily. Pour over some of the butter in the bottom of the cocotte. Top with chopped chives. Enjoy!