Cut lamb into 1 1/2-inch cubes; pat dry.
Heat oil in a kettle and brown lamb cubes. Sprinkle with salt, pepper, and flour then continue cooking, uncovered, over high heat, until well browned. Add beef broth and bring to a boil.
Add 1 chopped tomato, crushed garlic cloves, thyme, and bay leaf. Bring to a boil, lower the heat, and simmer covered for 45 minutes.
Meanwhile, in a skillet, saute sliced carrots, diced potatoes, and chopped onion in butter. Sprinkle with sugar then add to the lamb mixture. Bring again to a simmer, cover, and cook about 1 hour, or until the vegetables are tender.
Add frozen peas 5 minutes before done and heat through.