Preheat oven to 400f (200c)
Wash large russet potatoes and pat dry
Poke several holes in the potatoes with a fork and bake in the oven for 1 hour
Remove potatoes and let cool
While potatoes are cooking slice the onion very thin and add it to a large skillet over medium heat
Add 1 tbsp of butter and salt and cook until onions are nice and caramelized. About 30 minutes. Add garlic and cook another 3 minutes
Add 2 tbsp of butter, let it melt and then add the flour to the onions and cook for about 2 minutes.
Add Thyme and black pepper and then add the wine and beef broth to the pan. stir well to break up any clumps of flour.
Let simmer for several minutes until soup thickens
Cut top 1/3 off of baked potatoes and carefully scoop out most of the potato meat inside and place it in a bowl. Add remaining butter to the potato in the bowl and mash it all together.
Pour some french onion soup into the hollowed-out potatoes and then some of the mashed potato mixture and then a little more soup.
Cover the tops with generous amounts of the gruyere and parmesan cheese
Return your potatoes to the oven to melt the cheese. About 5-7 minutes.
Let cool slightly before serving
