Trim the stem end, cut in half lengthwise through the root and peel each half.

Leaving the root end intact, cut each half lengthwise in 1/4-inch-thick slices. Trim to remove the root.

Scatter the butter in the bottom of an electric slow cooker; at least 7qt capacity. Add the onions and sprinkle the thyme over the top. Place the lid on the slow cooker, set the cooking mode to high and set a timer for 2 hours.

Stir the onion mixture. Set a timer for 6 hours, continuing to cook on high. (I actually made mine overnight so set the temperature to low and the timer to 10 hours).

Turn the power off, remove the cover, give the onions a stir and let cool in the ceramic insert for 1 hour.

Cool completely, put into storage container and then cover and refrigerate for up to 5 days.

Heat the butter braised onions in a large pot until warmed,add the flour and cook for 2-3 minutes. Add the beef stock or broth and heat, stirring thoroughly til slightly thickened. Add the wine and season to taste.

Simmer partially covered for 20-25 minutes.

Correct seasoning. Set aside uncovered until ready to serve, then reheat to a simmer.

Just before serving, stir in the cognac.

Pour into individual bowls, add a couple of the toasted baguette rounds to the top and sprinkle with Parmesan cheese. Serve additional baguette slices on the side.