Cover potatoes with 1 inch water in a large saucepan. Bring to a boil, then reduce to simmer and cook until tender (about 15 minutes).

While potatoes are simmering, cook ground beef in a 12 inch skillet over medium heat, breaking up meat with a wooden spoon until almost cooked through (about 3 minutes).

Drain all but 1 Tablespoon fat from the skillet.

Return skillet to medium heat. Add onion and 1/2 teaspoon salt and cook until onion is softened, about 5 minutes.

Stir in flour and tomato paste and cook, stirring constantly, until flour is well blended (about 1 minute).

Slowly whisk in broth, thyme, and Worcestershire; scraping up browned bits. Bring to a simmer.

Return drained ground beef to skillet, cover, and cook over medium-low heat until sauce is thickened (6 to 8 minutes).

Drain potatoes, return to pot, and mash with a potato masher.

Stir in butter, then half-and-half. Season with salt and pepper to taste. Cover to keep warm.

Stir peas and carrots into beef mixture and simmer until heated through, about 2 minutes. Season with salt and pepper to taste.

Serve filling topped with mashed potatoes. Makes 4 servings.