Cut a quarter off of the top of each onions (the bottom side should have the dried roots exposed). Peel the onions. Using a melon baller carefully scoop out the onion leaving a double wall of onion. Set aside.
Finely chop the two cups of the removed onion.
Place 2 tablespoons of butter into a medium skillet along with the bacon, 2 cups of chopped onions, salt and 4 branches of thyme. Cook for 15 minutes over medium heat, stirring occasionally.
Add 1 tablespoon of butter to the onion mixture and let melt. Add the mushrooms and rice to the mixture and cook for 5 minutes. Stir occasionally. Remove from the heat and remove the thyme. Stir in the breadcrumbs and pour into a bowl.
Pour chicken stock into the skillet and add the 4 thyme springs and bay leaves. Place back onto the heat.
With the onion mixture, stuff the onions 3/4 of the way full, lightly packing the filling with a spoon. Place the stuffed onions into the skillet. Bring the stock to a boil and cover.
Place into the oven and let cook for 1 hour, basting the onions 3-4 times during the cooking process. Serve warm.
Notes
This recipe is an extension of Richard Olney’s Braised Onions from his cookbook, Simple French Food. I added rice and a few different herbs to the recipe. This recipe makes enough filling for at least 6 onions.