Limas and Spinach

2 C frozen lima beans
1 Tbsp vegetable oil
1 C fennel, cut in 4-oz strips
1/2 C onion, chopped
1/4 C low-sodium chicken broth
4 C leaf spinach, washed thoroughly
1 Tbsp distilled vinegar
1/8 tsp black pepper
1 Tbsp raw chives