Brussels Sprouts with Mustard, Thyme, and Lemon fr. Gourmet Magazine

2 tablespoons olive oil
1 small onion, thinly sliced
10 cups sliced brussels sprouts (halve each sprout and then cut into ¼-inch slices)
2 teaspoons salt
½ teaspoon freshly ground black pepper
1½ cups chicken or vegetable stock
1/3 cup Dijon mustard
2 tablespoons fresh thyme leaves plus additional sprigs for garnish
2 tablespoons lemon juice

Heat oil in large sauté pan over high heat. Add onion and sauté for 7-10 minutes until light golden brown. Add brussels sprouts, salt, and pepper and cook for 10 minutes more, stirring frequently. Add stock, bring to boil, and cook about 5 minutes. Mix in mustard, return to boil, and add thyme and lemon juice. Serve garnished with thyme sprigs. Serves 10.