• In a large frying pan, melt the butter over medium-high heat. Add the onions, fresh thyme, garlic, salt, and pepper and mix well. Reduce heat to medium and cook until the onions are soft and caramelized 30 minutes or so.
• Once caramelized, transfer the contents of the frying pan to a large stock pot to make the soup. Add the Beef Bone Stock or vegetable broth and wine. Bring to boil, reduce the heat, and simmer for 5 minutes, stirring often.
• While the soup is simmering, prepare your jars.
• Remove the pot from the heat and using tongs or a slotted spoon, evenly distribute the hot caramelized onions into hot jars, this will be about 2 cups per quart size jar. Ladle the hot broth over the onions, leaving 1inch of headspace.
• Wipe the rim of each jar with a warm dish towel dipped into white vinegar. Place a lid and ring on each jar and hand tighten.
• Add 1 inch of warm water to your pressure canner and add your jars. Lock the pressure canner lid and bring to a boil on high heat. Let the canner vent for 10 minutes. Close the vent and continue heating to achieve 11 PSI for a digital gauge or 10 PSI for a weighted gauge. Process jars for 1 hour and 15 minutes and pint size jars for 1 hour.
• Once the time has finished, turn off the heat but leave your pressure canner for a minimum of 3 hours, longer is better to allow the pressure canner to depressurize slowly and full before you remove the weight or open the lid.

Serving

• Open a jar or two, pour into a pot, heat over medium heat on the stove top. Once heated through, add soup to oven-safe bowls. Top with a slice of baguette or Rose Mary Croutons. Cover the bread with a slice of provolone and Swiss cheese for the best flavor, and place the bowls on a cookie baking sheet and broil in the oven until the cheese bubbles and browns slightly. Serve hot.