344 calories; 15.4 g fat; 4.9 g saturated fat; 55.1 mg cholesterol; 241 mg sodium; 30.5 g carbohydrate; 6.3 g fiber; 22.7 g protein
Preheat oven to 350°F.
If using ground beef, brown it in a large nonstick skillet and drain any excess fat. Remove from skillet and set aside.
Add oil to skillet and saute onions and carrots until tender, about 8 minutes. Add mushrooms and thyme, stirring occasionally, until mushrooms are soft, about 5 minutes.
Return meat to the pan (or add pot roast now). Add flour and cook for 2 minutes. Stir in broth, salt and pepper. Bring to a simmer and stir in peas.
Pour mixture into a baking dish.
Steam potatoes for 10 minutes. Add cauliflower and cook until potatoes and cauliflower are tender, about 15 more minutes. Drain water and mash until smooth. Add milk, butter, salt and pepper to taste.
Spread the potato mixture on top of the meat and bake for about 25 minutes, or until heated through.