Clean vegetables; trim ends of carrots, beans and peas. In a large pot bring 4 cups (1 L) water to a boil. Add vegetables and cover. Reduce heat to medium and cook vegetables until tender.
Meanwhile in a small saucepan bring cream and butter to just below the boiling point. Whisk in flour, and continue to stir until slightly thickened.
Drain vegetables, reserving 2 cups (500 mL) of cooking liquid. Add to cream mixture, and pour over vegetables. Garnish with chopped fennel (optional).