Melt half of the butter in your soup pot. Add the onions and cook over medium heat, stirring often for ten minutes or less until they are soft and on the verge of browning. Toss in the rest of the butter and all of the mushrooms. Cook another ten minutes or so. There will be a little fond in your pot.
Add your beef stock, the three asian ingredients, and the thyme.
Simmer for about one hour. Remove the now naked thyme stems and serve dressed with chives, green scallions or a glimpse of whatever is up your sleeve. First courses are all about seduction.