Move oven rack to the upper-middle position and heat the broiler.
Place the frozen hash browns in a large microwavable bowl and separate the shreds. (I pound them lightly with the back of a wooden spoon and they fall apart.) Toss them with 2 tbsp of the melted butter, 1 tsp salt and 1/4 tsp pepper. Microwave the potatoes, covered, until tender - 7 - 10 minutes on high.
Cook ground meat and onion in a large oven safe skillet until it is cooked, about 5 minutes. Drain fat off.
Stir thyme and flour into beef/onion mixture and cook about 1 minute. Add broth and Worcestershire sauce and cook about 6 - 8 minutes until thickened.
Add peas and carrots to beef mixture and simmer until heated, about a minute, and season with salt and pepper.
Scatter the cooked hash browns over the top of the beef mixture and brush with the rest of the butter.
Place the skillet unter the broiler and broil 3 - 5 minutes or until the potatoes have golden brown tips.