This soulful stew with crisp bread slices makes an elegant meal that can be prepared in less than 30 minutes. If you prefer, you can substitute an additional cup of stock for the wine.
Combine stock, wine, tomatoes, shallots, fennel bulb, crushed red pepper flakes, and salt in a large pot and bring to a boil over high heat. Reduce heat to medium and simmer, uncovered, until vegetables are tender, about 10 minutes.
Meanwhile, preheat the broiler. Slice baguette on an angle into about eight 3/4-inch slices. Place on a baking sheet and broil until toasted, about 1 minute per side. Rub toasts on both sides with cut side of garlic; discard any remaining garlic.
Stir Swiss chard into pot and cook until just tender, about 3 minutes. Add tilapia and shrimp and cook until just cooked through, about 5 minutes. Serve garnished with chopped fennel fronds and with toasts on the side.