Heat in a large heavy saucepan over medium heat:
Add and cook, stirring, until the vegetables are tender but not browned, 7 to 10 minutes:
Add and cook, stirring, 1 minute more:
Add, along with enough water to barely cover the vegetables:
Bring to a boil, then reduce the heat, cover, and simmer, stirring occasionally, until the sweet potatoes are just tender, 30 to 35 minutes. Add:
Cook for another 15 minutes. Place in a small bowl:
Add 1 cup of the stewing liquid, stir until smooth, and stir the mixture into the stew. Simmer for another 15 minutes. Season to taste with:
Serve with: