In a medium saucepan, combine the cream, broth, bay leaf, and salt and pepper. Add the onions and bring to a simmer over medium-high heat. Lower the heat to maintain a simmer and cook for about 20 to 25 minutes, until the onions are tender and the liquid has thickened somewhat into a sauce.
Remove the bay leaf, stir in the Parmesan (if using) and parsley, and turn into a serving bowl. Serve hot.
Notes
If you want to make these gluten-free onions a day or two ahead of time, you can reheat them in one of two ways. Either reheat them in a covered baking dish in a 350-degree oven for about 15 minutes, stirring occasionally or heat them in a pot over medium-low heat until warm throughout, also stirring occasionally. If you think of it, let the onions in their sauce come to room temperature before reheating them.