Rinse fennel; cut in half and slice crosswise. In medium saucepan, over medium-high heat, cook bacon until crisp. Lift out bacon and discard all but 1 tablespoon of drippings.
Add onion and cook 2 minutes. Add fennel, potatoes and broth. Cover and simmer until potatoes and fennel are tender, about 20 minutes. Mash slightly with potato masher or leave chunks. Add bacon pieces. Season to taste with salt and pepper.