Slice the carrots 1/2-inch thick on an angle.
Quarter the fennel bulbs lengthwise, cut into bulb to remove core and thinly slice, or roughly chop. Reserve 1/4 cup chopped fennel fronds.
Halve and slice the onion. Fill a skillet with 1/4-inch water. Add vegetables then sprinkle with sugar and salt and drizzle with 2 tablespoons extra-virgin olive oil. Simmer covered 20 minutes, and uncovered for 5 minutes and adjust salt. Toss vegetables with fennel fronds, dill and chives.